string.hpp

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//==================================================================================================
/// \file
/// This header-file is part of module \alib_strings of the \aliblong.
///
/// Copyright 2013-2026 A-Worx GmbH, Germany.
/// Published under #"mainpage_license".
//==================================================================================================
 
//##################################################################################################
// forward declarations
//##################################################################################################
ALIB_EXPORT namespace alib::strings {
template<typename TChar>
requires alib::characters::IsCharacter<TChar> class  TString;
template<typename TChar>                      class  TCString;
template<typename TChar>                      class  TSubstring;
template<typename TChar, typename TAllocator>
requires alib::lang::IsAllocator<TAllocator>  class  TAString;
template<typename TChar>                      struct TNumberFormat;
}
 
ALIB_EXPORT namespace alib::strings {
 
/// This the type trait is tested by implicit "auto cast" operators.
/// Those might be disabled for specific combinations of types.
///
/// For example, implicit casting from class #"%AString" to sibling types #"%CString" and
/// #"%^Substring" has to be forbidden, because both are also constructible implicitly from
/// this class and hence an ambiguity between implicit cast and implicit construction would
/// arise.
///
/// Custom classes (i.e., if derived from class #"str TAString") might encounter
/// similar problems.
/// In that case, this type-traits type may be specialized to mitigate compilation issues.
///
/// @tparam TFrom        The type that allows implicit auto-casts.
/// @tparam TImOrExplict Denotes if implicit or explicit casts are suppressed.
/// @tparam TTo          The destination type that auto-casts should be suppressed for.
template<typename             TFrom,
         characters::Policy   TImOrExplict,
         typename             TTo>
struct NoAutoCastTraits : std::false_type   {};
 
// specializations for AString and CString
template<typename TChar, typename TAllocator>  struct NoAutoCastTraits<TAString<TChar, TAllocator>, characters::Policy::Implicit,   TCString<TChar> > : std::true_type {};
template<typename TChar, typename TAllocator>  struct NoAutoCastTraits<TAString<TChar, TAllocator>, characters::Policy::Implicit, TSubstring<TChar> > : std::true_type {};
template<typename TChar>                       struct NoAutoCastTraits<TCString<TChar>            , characters::Policy::Implicit, TSubstring<TChar> > : std::true_type {};
 
 
/// The maximum length of an \alib string.
inline constexpr integer  MAX_LEN = (std::numeric_limits<integer>::max)();
 
//==================================================================================================
/// This class is the base class of all #"alib_strings_classes;ALib string classes".
/// Objects of this type represent character strings whose data is allocated outside their scope.
/// In particular, the class does not allocate a character array buffer to store and manipulate
/// string data.
///
/// Once constructed, objects of this class are immutable, except for the possibility to assign
/// a complete new object value.
/// This means there is no interface to change the single two data members #".buffer" and
/// #".length".
/// The immutable nature of this type is lifted by derived types.
/// While the class #"^Substring" allows changing the start and length of the string represented,
/// class #"^AString" holds a copy of the data and consequently allows modifying the string stored.
///
/// \see
///   For an introduction into the \alib string classes see this module's
///   #"alib_mod_strings;Programmer's Manual".
///
/// @tparam TChar The #"alib_characters_chars;character type" of this string.
///         Alias names for specializations along the different character types
///         are provided in namespace #"alib" with type definitions
///         #"alib::String",
///         #"alib::NString",
///         #"alib::WString",
///         #"alib::XString",
///         #"alib::ComplementString", and
///         #"alib::StrangeString".
//==================================================================================================
template<typename TChar>
requires alib::characters::IsCharacter<TChar>
class TString {
  public:
    /// Exposes template parameter \p{TChar} to the outer world in a \c std compatible way.
    using value_type = TChar;
 
    /// The type defining sizes of strings.
    using size_type  = integer;
 
    // Debug warnings
    #if ALIB_DEBUG_STRINGS && !DOXYGEN
    void     dbgCheck()                                                                       const;
    #endif
 
  //################################################################################################
  // protected fields
  //################################################################################################
  protected:
    #if !DOXYGEN
    union {
        const TChar*   buffer;
              TChar*  vbuffer;
    };
    #else
        /// Pointer to an array of constant character values.
        /// This array holds the string that an instance of this type is representing.<br>
        /// Read access to this field is granted with the method #"Buffer".
        ///
        /// For technical reasons, this documentation unfortunately omits the important fact that
        /// this field is part of an anonymous union declared like this:
        ///
        ///      union
        ///      {
        ///          const TChar*   buffer;
        ///                TChar*  vbuffer;
        ///      };
        ///
        /// Hence, the field can also be interpreted as a pointer to an array of <b>non-constant</b>
        /// character values.
        /// Derived classes might use the sibling version \b vbuffer to modify the contents of
        /// the string if it is assured that such memory is writable.
        /// This is, for example, done extensively by the implementation of class #"^AString".
        ///
        /// \note
        ///   It might not be considered pure/nice OO-design to prepare a feature of specialized
        ///   classes in a non-abstract base class, as done here. But the alternative would have
        ///   been to force derived classes to perform re-interpret casts or even worse tricks
        ///   to rightfully access a writeable buffer.
        const TChar*   buffer;
    #endif
 
    /// The length of the character string represented.
    /// Read access to this field is granted with the method #".Length".
    integer         length;
 
  //################################################################################################
  // Constructors
  //################################################################################################
  public:
 
    /// Defaulted default constructor. Leaves this instance \b uninitialized and undefined.
    /// In other words, the methods #"Buffer" and #".Length" give random results.
    constexpr TString()                                                           noexcept =default;
 
    /// Defaulted copy constructor
    constexpr TString(const TString&)                                             noexcept =default;
 
    /// Defaulted move constructor
    constexpr TString(     TString&&)                                             noexcept =default;
 
    /// Defaulted copy assignment operator.
    /// @return A reference to <c>this</c> instance.
    constexpr TString& operator=(const TString&)                                  noexcept =default;
 
    /// Defaulted move assignment operator.
    /// @return A reference to <c>this</c> instance.
    constexpr TString& operator=(     TString&&)                                  noexcept =default;
 
 
    /// Constructor accepting a pointer to a character array and a string length.
    ///
    /// @param pBuffer   Pointer to the start of the character string to represent.
    /// @param pLength   The length of the character string to represent.
    constexpr   TString( const TChar* pBuffer, integer pLength )                            noexcept
    : buffer(pBuffer)
    , length(pLength)                                                                             {}
 
    /// Constructor accepting \c nullptr. Constructs a nulled string.
    constexpr           TString(lang::IsNullptr auto const &)                               noexcept
    : buffer( nullptr ), length( 0       )                                                        {}
 
// Doxygen (V1.15) would create identical entries in its tag-file, so those are not reachable.
// On the other hand, it complains if the methods are not doxed. So, we hide them from doxygen.
#if DOXYGEN
    /// Templated \b implicit constructor accepting a \c const reference to an object of a
    /// type that satisfies the concepts #"IsImplicitArraySource" or
    /// #"IsExplicitArraySource".
    ///
    /// Custom types can be enabled for this constructor by specializing the traits-type
    /// #"ArrayTraits", which is used for both;
    /// the implementation of the concept, and
    /// the implementation of this constructor itself.
    ///
    /// @tparam T    The type of the given \p{src}.
    ///              Requires satisfying the concept #"IsImplicitArraySource".
    ///              Deduced by the compiler.
    /// @param  src  The source of the string data to copy.
    template <typename T>
    constexpr           TString(const T& src)                                              noexcept;
#else
    template <typename T>
    requires alib::characters::IsImplicitArraySource<T, TChar>
    constexpr           TString(const T& src)                                               noexcept
    : buffer( characters::ArrayTraits<std::remove_cv_t<T>,TChar>::Buffer( src ) )
    , length( characters::ArrayTraits<std::remove_cv_t<T>,TChar>::Length( src ) )                 {}
 
    template<typename T>
    requires alib::characters::IsExplicitArraySource<T, TChar>
    constexpr explicit  TString(const T& src)                                               noexcept
    : buffer( characters::ArrayTraits<std::remove_cv_t<T>,TChar>::Buffer( src ) )
    , length( characters::ArrayTraits<std::remove_cv_t<T>,TChar>::Length( src ) )                 {}
#endif
    /// Templated \b explicit constructor accepting a \b mutable reference to an object of a
    /// type that satisfies the concept #"IsMutableArraySource".
    ///
    /// Custom types can be enabled for this constructor by specializing the traits-type
    /// #"ArrayTraits", which is used for both;
    /// the implementation of the concept, and
    /// the implementation of this constructor itself.
    ///
    /// @tparam T    The type of the given \p{src}.
    ///              Requires satisfying the concept #"IsMutableArraySource".
    ///              Deduced by the compiler.
    /// @param  src  The source of the string data to copy.
    template<typename T>
    requires alib::characters::IsMutableArraySource<T, TChar>
    constexpr explicit  TString(      T& src)                                               noexcept
    : buffer( characters::ArrayTraits<std::remove_cv_t<T>,TChar>::Buffer( src ) )
    , length( characters::ArrayTraits<std::remove_cv_t<T>,TChar>::Length( src ) )                 {}
 
    /// Constructor which allocates memory, copies the given string's contents, and
    /// lets this string represent this new character array.<br>
    /// Note that it is up to the using code to duly deallocate the memory, because the
    /// destructor of this type does not do so.
    /// @see Methods #".Allocate" and #".Free" for information how to use allocated string objects.
    ///
    /// @tparam TAllocator The type of the given \p{allocator}, as prototyped with class
    ///                    #"lang::Allocator".
    ///                    Requires satisfying the concept #"IsAllocator".
    ///                    Deduced by the compiler.
    /// @param  allocator  The allocator to use.
    /// @param  copy       The string to copy to the new memory allocated.
    template<typename TAllocator>
    requires alib::lang::IsAllocator<TAllocator>
    TString( TAllocator& allocator, const TString<TChar>& copy ) {
        if( (length= copy.length) == 0 ) {
            buffer= copy.buffer;
            return;
        }
 
        auto* newBuf=  allocator().template AllocArray<TChar>( copy.length);
        copy.CopyTo( newBuf );
        buffer= newBuf;
    }
 
  //######################################### casting  back ########################################
  // Doxygen (V1.15) would create identical entries in its tag-file, so those are not reachable.
  // On the other hand, it complains if the methods are not doxed. So, we hide them from doxygen.
  #if DOXYGEN
    /// Templated \b implicit <c>cast operator</c> constructing an instance of type \p{T} from
    /// this string instance.
    /// This operator requires the type \p{T} satisfying the concepts
    /// #"IsImplicitArrayCast" and #"IsExplicitArrayCast".
    ///
    /// Custom types can be enabled for this operator by specializing the traits-type
    /// #"ArrayTraits", which is used for both;
    /// the implementation of the concept, and
    /// the implementation of this operator itself.
    ///
    /// @tparam T    The type to implicitly cast this instance to.
    ///              Requires satisfying the concept #"IsImplicitArrayCast".
    ///              Deduced by the compiler.
    /// @return A value of type \p{T}.
    template< typename T>
    constexpr           operator T()                                                          const;
#else
    template< typename T>
    requires (     alib::characters::IsImplicitArrayCast<T, TChar>
               && !alib::strings::NoAutoCastTraits< TString<TChar>,
                                                    characters::Policy::Implicit,
                                                    std::remove_cv_t<T> >::value )
 
    constexpr           operator T()                                                           const
    { return characters::ArrayTraits<T,TChar>::Construct( buffer, length );  }
 
    template< typename T>
    requires  (     alib::characters::IsExplicitArrayCast<T, TChar>
                && !alib::strings::NoAutoCastTraits< TString<TChar>,
                                                     characters::Policy::ExplicitOnly,
                                                     std::remove_cv_t<T>     >::value )
    constexpr explicit  operator T()                                                           const
    { return characters::ArrayTraits<T,TChar>::Construct( buffer, length ); }
#endif
 
  //################################################################################################
  //  Buffer Access, Length, and State
  //################################################################################################
 
    /// Returns a pointer to the first character of the string we are representing.
    /// \note The string is not guaranteed to be zero-terminated.
    ///
    /// @return The start of the character array comprising the string represented by this
    ///         object.
    constexpr const TChar*  Buffer()                                        const { return buffer; }
 
    /// Returns the length of the string that this object represents.
    ///
    /// @return The length of the string represented by this object.
    constexpr integer       Length()                                        const { return length; }
 
    /// Returns the length of the string if represented as a wide character string.
    /// If template parameter \p{TChar} equals \c wchar, then this is identical with #".Length".
    /// Otherwise the calculation is done using
    /// - <em>mbsnrtowcs()</em>
    ///   (without providing a conversion buffer) on glibc platforms (e.g., Linux)
    /// - <em>MultiByteToWideChar()</em>
    ///   (without providing a conversion buffer) on the Windows platform.
    ///
    /// If the conversion fails, \c -1 is returned.
    ///
    /// \note
    ///   On GNU/Linux and Mac OS, it might be necessary to invoke standard C method
    ///   <em>setlocale()</em> once, before using this method, to successfully calculate
    ///   the length.
    ///   This by default is done during #"alib_mod_bs;library initialization",
    ///   if performed on class #"BASECAMP;2".
    ///
    /// @return The length of string when it was converted to wide characters.
    ///         If counting failed (what means that a corresponding conversion would also fail)
    ///         the #".Length" is returned.
    integer                 WStringLength()                                                   const;
 
 
    /// Returns \c true if field #".buffer" equals \c nullptr, \c false otherwise.
    /// Note that a \e nulled string is also considered #"IsEmpty;empty".
    ///
    /// \see
    ///   Details on the concept of \e nulled and \e empty strings are documented in chapter
    ///   #"alib_strings_details_nulled_vsempty" of this module's
    ///   #"alib_mod_strings;Programmer's Manual".
    ///
    /// @return \c true if no buffer is allocated.
    constexpr bool          IsNull()                             const { return buffer == nullptr; }
 
    /// Returns \c true if field #".buffer" does not equal \c nullptr, \c false otherwise.
    ///
    /// @return The negated value of method #".IsNull".
    constexpr bool          IsNotNull()                          const { return buffer != nullptr; }
 
    /// Returns \c true if this string is of zero length.
    /// Note that a \e nulled string is also considered empty.
    ///
    /// \see
    ///   Details on the concept of \e nulled and \e empty strings are documented in chapter
    ///   #"alib_strings_details_nulled_vsempty" of this module's
    ///   #"alib_mod_strings;Programmer's Manual".
    /// @return \c true if the actual length equals zero.
    constexpr bool          IsEmpty()                                  const { return length == 0; }
 
    /// Returns \c true if this string has a length of \c 1 or more.
    /// @return \c true if the actual length does not equal zero.
    constexpr bool          IsNotEmpty()                               const { return length != 0; }
 
 
 
 
    /// Returns a new string object representing a substring of the string that this object
    /// represents.
    ///
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If \c false is given, no range check is performed.
    /// @param  regionStart  The start of the substring within this string.
    /// @param  regionLength The length of the substring to return.
    ///                      Defaults to #"str MAX_LEN".
    /// @return A string representing a region of this string.
    template <typename TCheck= CHK>
    TString<TChar>   Substring(integer regionStart, integer regionLength =MAX_LEN )          const {
        ALIB_STRING_DBG_CHK(this)
 
        if constexpr ( TCheck::value ) {
            AdjustRegion( regionStart, regionLength );
        } else {
            #if ALIB_DEBUG
                integer rs= regionStart;
                integer rl= regionLength;
                AdjustRegion( rs, rl );
                ALIB_ASSERT_ERROR( rs == regionStart && rl == regionLength, "STRINGS",
                  "Non-checking invocation: ", "Invalid region {}/{} given. Adjusted: {}/{}",
                  regionStart, regionLength, rs, rl )
            #endif
        }
 
        return TString<TChar>( buffer + regionStart, regionLength );
    }
 
  //################################################################################################
  //  Character Access
  //################################################################################################
 
    /// Retrieves the character at the given index. A range check is performed. If this fails,
    /// \c '\0' is returned.
    ///
    /// @tparam TCheck  Defaults to #"CHK;2", which is the normal invocation mode.
    ///                 If \c false is given, no range check is performed.
    /// @param idx      The index of the character to read.
    /// @return The character at the given index, or '\0' if index out of range.
    template <typename TCheck= CHK>
    TChar        CharAt( integer idx )                                                       const {
        if constexpr ( TCheck::value )
            return  ( idx >= 0 && idx < length ) ? *(buffer + idx )
                                                 : '\0' ;
        ALIB_ASSERT_ERROR( idx >= 0 && idx < length, "STRINGS",
                           "Non checking version: Index out of range: 0 <= {} < {}.", idx, length )
 
        return  *(buffer + idx );
    }
 
    /// Retrieves the first character.
    /// In the case of an empty or \e nulled string, '\0' is returned.
    ///
    /// @tparam TCheck  Defaults to #"CHK;2", which is the normal invocation mode.
    ///                 If #"NC" is given, no check for an empty string object is performed.
    /// @return The first character of the #"%^String".
    ///         If this instance's length is zero,  '\0' is returned.
    template <typename TCheck= CHK>
    TChar        CharAtStart()                                                               const {
        if constexpr ( TCheck::value )
            return length > 0  ?  *(buffer)
                               :  '\0';
 
        ALIB_ASSERT_ERROR( length > 0, "STRINGS", "Non checking invocation on empty string" )
        return  *(buffer);
    }
 
 
    /// Retrieves the last character. In the case of an empty string, '\0' is returned.
    ///
    /// @tparam TCheck  Defaults to #"CHK;2", which is the normal invocation mode.
    ///                 If #"NC" is given, no check for an empty or \e nulled object is
    ///                 performed.
    ///
    /// @return The last character of the #"%^String".
    ///         If this instance's length is zero,  '\0' is returned.
    template <typename TCheck= CHK>
    TChar        CharAtEnd()                                                                 const {
            if constexpr ( TCheck::value )
                return length > 0   ?  *(buffer + length - 1)
                                    : '\0';
 
            ALIB_ASSERT_ERROR( length > 0, "STRINGS", "Non checking invocation on empty string" )
            return  *(buffer + length - 1);
    }
 
    /// Reads a character at a given index.
    ///
    /// \note
    ///   Unlike method #"TString::CharAt", this operator does <em>not</em> perform do range check on
    ///   parameter \p{idx}.
    ///   The rationale for this is that derived mutable types (e.g., class #"%AString"),
    ///   may provide a mutable (non-<c>const</c>) version of this operator, returning a
    ///   reference to the character to provide write access. Such reference
    ///   to a character could not be given if the index was out of range.
    ///   This way, a check in the derived type could likewise not be implemented.
    ///
    /// \note
    ///   As a result, this operator is equivalent to a call to the non-checking version of method
    ///   #"TString::CharAt;CharAt<NC>". For safe access to characters in the buffer use
    ///   #"TString::CharAt;CharAt<CHK>" which returns <c>'\0'</c> in the case of that \p{idx} is out of
    ///   bounds.
    ///
    /// \note
    ///   Still, in debug-compilations this operator #"alib_mod_assert;raises an ALib error"
    ///   if \p{idx} is out of bounds.
    ///
    /// @param   idx    The index of the character within this object's buffer.
    /// @returns If the character contained at index \p{idx}.
    TChar    operator[] (integer idx)                                                        const {
        ALIB_ASSERT_ERROR( idx >= 0  && idx < length, "STRINGS",
                           "Index out of bounds: 0 <= {} < {}.", idx, length )
        return buffer[idx];
    }
 
  //################################################################################################
  //  Hashing
  //################################################################################################
    /// Computes a hash number for the contained string.
    ///
    /// \note
    ///   If this library is compiled using C++17, internally this method is using
    ///   <c>std::hash<std::string_view<TChar>></c>. Otherwise a compatible hash function
    ///   is used.
    /// \see Alternative method #".HashcodeIgnoreCase".
    ///
    /// @return A hash number which is equal for two instances with the same content.
    std::size_t Hashcode()                                                                    const;
 
    /// Computes a hash number for the contained string converted to upper case letters.
    ///
    /// \see Alternative method #".Hashcode".
    ///
    /// @return A hash number which is equal for two instances with have the same content
    ///         if converted to upper case letters.
    std::size_t HashcodeIgnoreCase()                                                          const;
 
  //################################################################################################
  //  Comparison Methods
  //################################################################################################
    /// Compares this string with a
    /// #"alib_strings_cc_construction_string;string-like object".
    ///
    /// \c true is returned if this and the compared string are \e nulled or empty.
    /// If only one is \e nulled or empty, \c false is returned.
    ///
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If #"NC" is given, no check for a \e nulled is performed
    ///                      on this string as well as on \p{rhs}.
    /// @tparam TSensitivity Determines if comparison is case-sensitive (the default) or not.
    /// @param  rhs          The object to compare.
    ///
    /// @return \c true, if the contents of this string and the string representation of the
    ///         given \p{rhs} are equal.
    template <typename   TCheck       = CHK,
              lang::Case TSensitivity = lang::Case::Sensitive>
    bool Equals( const TString<TChar>& rhs )                                                 const {
        ALIB_STRING_DBG_CHK(this)
 
        if constexpr ( TCheck::value ) {
            if ( IsNull() &&  rhs.IsNull() )
                return true;
 
            if (  ( IsNull() !=  rhs.IsNull() )    )
                return false;
        }
        #if ALIB_DEBUG
        else
        {   // we do not use IsNull() here, for not having a call noted in performance tools
            ALIB_ASSERT_ERROR(     buffer != nullptr,"STRINGS", "Non checking but this is nulled." )
            ALIB_ASSERT_ERROR( rhs.buffer != nullptr,"STRINGS", "Non checking but rhs is nulled."  )
        }
        #endif
 
        if ( length != rhs.length )
            return false;
 
        if ( length == 0 )
            return true;
 
        if constexpr (TSensitivity == lang::Case::Sensitive ) {
            // note: this warning 'suddenly' needed to be silenced with GCC 14.2.1, but only in
            //       release builds, in cases where TCheck was true, and thus null-checks
            //       were performed, and in fact this code was not reached.
            ALIB_ALLOW_NULL_POINTER_PASSING
            return  characters::Equal            ( buffer, rhs.buffer, length );
            ALIB_POP_ALLOWANCE
        }
        else
            return  characters::CompareIgnoreCase( buffer, rhs.buffer, length ) == 0;
    }
 
    /// Compares this string with a
    /// #"alib_strings_cc_construction_string;string-like object".
    ///
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If #"NC" is given, no check for a \e nulled object (this) is
    ///                      performed and this string must not be of zero length
    ///                      (while \p{rhs} might be of zero length).
    /// @tparam TSensitivity Determines if comparison is case-sensitive (the default) or not.
    /// @param  rhs          The object to compare.
    ///
    /// @return
    ///   -  0 if this and \p{rhs} are \e nulled or if both have a length of 0 or if both
    ///        share the same content
    ///   - <0 if this is \e nulled and \p{rhs} is not or if this is smaller than \p{rhs}.
    ///   - >0 if this is not \e nulled but \p{rhs} is or if this is greater than \p{rhs}.
    template <typename   TCheck       = CHK,
              lang::Case TSensitivity = lang::Case::Sensitive>
    int CompareTo( const TString<TChar>& rhs )                                               const {
        ALIB_STRING_DBG_CHK(this)
 
        // check \c nullptr arguments
        if (TCheck::value &&     IsNull() )  return  rhs.IsNull() ? 0 : -1;
        if (TCheck::value && rhs.IsNull() )  return  +1;
 
        // zero length ?
        if ( TCheck::value && length == 0 )  return  rhs.length == 0 ? 0 : -1;
        if (              rhs.length == 0 )  return +1;
 
        bool    thisIsShorter=  ( length < rhs.length);
        integer shortLen  = thisIsShorter ? length : rhs.length;
 
        int cmpVal=  (TSensitivity == lang::Case::Sensitive)
                     ? characters::Compare          ( buffer, rhs.buffer, shortLen )
                     : characters::CompareIgnoreCase( buffer, rhs.buffer, shortLen );
 
        if ( cmpVal != 0 || length == rhs.length )
            return cmpVal;
        return thisIsShorter ? -1 : 1;
    }
 
    /// Compares this string with a region of another
    /// #"alib_strings_cc_construction_string;string-like object".
    ///
    /// @tparam TCheck         Defaults to #"CHK;2", which is the normal invocation mode.
    ///                        If #"NC" is given, no check for a \e nulled comparison
    ///                        object is performed and this string must not be empty.
    ///                        Furthermore, no check is performed whether the given region
    ///                        fits to parameter \p{rhs}. This also means that the default
    ///                        value must not be used with <em>TCheck==#"NC"</em>.
    /// @tparam TSensitivity   Determines if comparison is case-sensitive (the default) or not.
    /// @param rhs             The string to compare this string with.
    /// @param rhsRegionStart  The start of the region in \p{rhs} to compare this object
    ///                        with.
    /// @param rhsRegionLength The length of the region in \p{rhs} to compare this object
    ///                        with.
    ///                        Defaults to #"str MAX_LEN".
    ///
    /// @return
    ///   -  0 if this and \p{rhs} are \e nulled or if both have a length of 0 or if both
    ///        share the same content
    ///   - <0 if this is \e nulled and \p{rhs} is not or if this is smaller than \p{rhs}.
    ///   - >0 if this is not \e nulled but \p{rhs} is or if this is greater than \p{rhs}.
    template < typename   TCheck       = CHK,
               lang::Case TSensitivity = lang::Case::Sensitive>
    int CompareTo(  const TString&  rhs,
                    integer         rhsRegionStart,
                    integer         rhsRegionLength   =MAX_LEN  )                            const {
        if constexpr ( TCheck::value ) {
            TString cmpSub( rhs.buffer, 0);
            rhs.AdjustRegion( rhsRegionStart, rhsRegionLength );
            cmpSub.buffer+=   rhsRegionStart;
            cmpSub.length=    rhsRegionLength;
 
            return CompareTo<CHK,  TSensitivity>( cmpSub );
        }
        else
            return CompareTo<NC, TSensitivity>( TString( rhs.buffer + rhsRegionStart,
                                                            rhsRegionLength ) );
    }
 
    /// Compares a region of this object with a region of another
    /// #"alib_strings_cc_construction_string;string-like object".
    ///
    /// @tparam TCheck         Defaults to #"CHK;2", which is the normal invocation mode.
    ///                        If #"NC" is given, no check for a \e nulled comparison
    ///                        object is performed and this string must not be empty.
    ///                        Furthermore, no check is performed whether the given regions fit
    ///                        to this object respectively the other region to the object given
    ///                        with parameter \p{rhs}.
    ///                        This also means that the default value of \p{regionLength} must
    ///                        not be used in this case.
    /// @tparam TSensitivity   Determines if comparison is case-sensitive (the default) or not.
    /// @param rhs             The string to compare this string with.
    /// @param rhsRegionStart  The start of the region in \p{rhs} to compare this object
    ///                        with.
    /// @param rhsRegionLength The length of the region in \p{rhs} to compare this object
    ///                        with.
    /// @param regionStart     The start of the region in this object to compare with
    /// @param regionLength    The length of the region in this object to compare with.
    ///                        Defaults to #"str MAX_LEN".
    ///
    /// @return
    ///   -  0 if this and \p{rhs} are \e nulled or if both have a length of 0 or if both
    ///        share the same content
    ///   - <0 if this is \e nulled and \p{rhs} is not or if this is smaller than \p{rhs}.
    ///   - >0 if this is not \e nulled but \p{rhs} is or if this is greater than \p{rhs}.
    template < typename   TCheck       = CHK,
               lang::Case TSensitivity = lang::Case::Sensitive>
    int CompareTo(  const TString&  rhs,
                    integer            rhsRegionStart,
                    integer            rhsRegionLength,
                    integer            regionStart,
                    integer            regionLength      =MAX_LEN  )                         const {
        if constexpr ( TCheck::value ) {
            TString cmpSub( rhs.buffer, 0);
            rhs.AdjustRegion( rhsRegionStart, rhsRegionLength );
            cmpSub.buffer+=   rhsRegionStart;
            cmpSub.length=    rhsRegionLength;
 
            AdjustRegion( regionStart, regionLength );
            return TString( buffer + regionStart, regionLength ).CompareTo<CHK, TSensitivity>( cmpSub );
        }
 
        return TString( buffer + regionStart, regionLength )
                .CompareTo<NC, TSensitivity>( TString( rhs.buffer + rhsRegionStart,
                                                          rhsRegionLength )               );
    }
 
    /// Returns \c true, if the contents of the given
    /// #"alib_strings_cc_construction_string;string-like object" is found at the given
    /// position.
    ///
    /// \note
    ///   The following rules apply:
    ///   - If \p{pos} is out of range or \p{needle} is \e nulled, \c false is returned.
    ///     (This check only done if \p{TCheck} equals #"CHK;2".)
    ///   - Otherwise, if the length of \p{needle} is 0, \c true is returned.
    ///
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If \c <false> is given, no check on parameter
    ///                      \p{pos} is performed and \p{needle} must not be \e nulled.
    /// @tparam TSensitivity Determines if comparison is case-sensitive (the default) or not.
    /// @param needle        The string to compare with. If it is #"IsEmpty;empty", \c true
    ///                      is returned.
    /// @param pos           The position to search for needle.
    /// @return \c true if \p{needle} is found at the given position. False otherwise.
    template< typename    TCheck       = CHK,
              lang::Case  TSensitivity = lang::Case::Sensitive >
    bool ContainsAt( const TString& needle, integer pos )                                    const {
        integer needleLength= needle.length;
        ALIB_STRING_DBG_CHK(this)
        if constexpr ( TCheck::value ) {
            if ( pos < 0 || pos + needleLength > length || needle.IsNull () )
                return false;
            if ( needleLength == 0 )
                return true;
        } else {
            ALIB_ASSERT_ERROR( pos >= 0 && pos + needleLength <= length,
                               "STRINGS", "Non checking and index out of range: 0 <= {}, {} <= {}.",
                                          pos, pos + needleLength, length )
            ALIB_ASSERT_ERROR( needleLength != 0,
                               "STRINGS", "Non checking and emtpy compare string" )
        }
 
        return TSensitivity == lang::Case::Sensitive
               ? characters::Equal            ( buffer + pos,  needle.buffer, needleLength )
               : characters::CompareIgnoreCase( buffer + pos,  needle.buffer, needleLength ) == 0 ;
    }
 
    /// Returns \c true, if this string starts with the contents of the
    /// #"alib_strings_cc_construction_string;string-like object" given with parameter
    /// \p{needle}.
    /// In the special case that \p{needle} is #"IsEmpty;empty", \c true is returned.
    ///
    /// @tparam TSensitivity Determines if comparison is case-sensitive (the default) or not.
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If \c <false> is given, the given needle must not be empty
    ///                      and must not be longer than this string!
    ///                      \p{pos} is performed and \p{needle} must not be \e nulled.
    /// @param needle        The string to compare the start of this string with.
    ///                      If \e nulled or empty, \c true is returned.
    /// @return \c true if \p{needle} is found at the start of this string, \c false otherwise.
    template<typename    TCheck       = CHK,
             lang::Case  TSensitivity =lang::Case::Sensitive>
    bool StartsWith( const TString& needle )                                                 const {
        if constexpr ( TCheck::value ) {
            if ( needle.length > length )
                return false;
            if ( needle.length == 0 )
                return true;
        } else {
            ALIB_ASSERT_ERROR( needle.length <= length, "STRINGS",
                               "Non checking and needle longer than this string: {} > {}",
                               needle.length, length )
            ALIB_ASSERT_ERROR( needle.length != 0     , "STRINGS",
                               "Non checking and emtpy needle given." )
        }
 
        if constexpr ( TSensitivity == lang::Case::Sensitive )
            return  characters::Equal            ( buffer,  needle.buffer, needle.length );
        else
            return  characters::CompareIgnoreCase( buffer,  needle.buffer, needle.length ) == 0;
    }
 
    /// Returns \c true, if this string ends with the string found in parameter \p{needle}.
    /// If \p{needle} is #"IsEmpty;empty", \c true is returned.
    ///
    /// @tparam TSensitivity Determines if comparison is case-sensitive (the default) or not.
    /// @param needle        The string to compare the end of this string with.
    ///                      If \e nulled or empty, \c true is returned.
    /// @return \c true if \p{needle} is found at the end of this, \c false otherwise.
    template<typename    TCheck       = CHK,
             lang::Case  TSensitivity =lang::Case::Sensitive>
    bool EndsWith( const TString& needle )                                                   const {
        if constexpr ( TCheck::value ) {
            if ( needle.length > length )
                return false;
            if ( needle.length == 0 )
                return true;
        } else {
            ALIB_ASSERT_ERROR( needle.length <= length, "STRINGS",
                               "Non checking and needle longer than this string: {} > {}",
                               needle.length, length )
            ALIB_ASSERT_ERROR( needle.length != 0     , "STRINGS",
                               "Non checking and emtpy needle given." )
        }
 
        if constexpr ( TSensitivity == lang::Case::Sensitive )
            return characters::Equal            ( buffer + length - needle.length,  needle.buffer, needle.length );
        else
            return characters::CompareIgnoreCase( buffer + length - needle.length,  needle.buffer, needle.length ) == 0;
    }
 
  //################################################################################################
  //  Search
  //################################################################################################
 
    /// Searches a character starting from a given position.
    ///
    /// @tparam TCheck   Defaults to #"CHK;2", which is the normal invocation mode.
    ///                  If \c false is given, no range check is performed.
    /// @param needle    The character to search for.
    /// @param startIdx  The index in this to start searching the character.
    ///                  Defaults to \c 0.
    ///
    /// @return \c -1 if the character \p{needle} is not found.
    ///         Otherwise the index of its first occurrence.
    template <typename TCheck= CHK>
    integer  IndexOf( TChar needle, integer startIdx = 0 )                                   const {
        ALIB_STRING_DBG_CHK(this)
 
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
                 if ( startIdx <  0      )  startIdx= 0;
            else if ( startIdx >= length )  return -1;
        } else {
            ALIB_ASSERT_ERROR( startIdx >= 0 && startIdx < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startIdx, length )
        }
 
        const TChar* result=  characters::Search( buffer + startIdx, length - startIdx, needle );
 
        return result != nullptr ? result  -  buffer
                                 : -1;
    }
 
    /// Searches a character within a region of this.
    ///
    /// @tparam TCheck      Defaults to #"CHK;2", which is the normal invocation mode.
    ///                     If \c false is given, no range check is performed.
    /// @param needle       The character to search for.
    /// @param regionStart  The start of the region to search the character in.
    /// @param regionLength The length of the region to search the character in.
    /// @return \c -1 if the character \p{needle} is not found.
    ///         Otherwise the index of its first occurrence.
    template <typename TCheck= CHK>
    integer         IndexOf( TChar needle, integer regionStart, integer regionLength )       const {
        ALIB_STRING_DBG_CHK(this)
 
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
            if ( AdjustRegion( regionStart, regionLength ) )
                return -1;
        } else {
            #if ALIB_DEBUG
                integer rs= regionStart;
                integer rl= regionLength;
                ALIB_ASSERT_ERROR(     !AdjustRegion( rs, rl )
                                    && rs == regionStart && rl == regionLength,  "STRINGS",
                    "Non-checking invocation: ", "Invalid region {}/{} given. Adjusted: {}/{}",
                    regionStart, regionLength, rs, rl )
            #endif
        }
 
        const TChar* result=  characters::Search( buffer + regionStart, regionLength, needle );
 
        return result != nullptr ? result  -  buffer
                                 : -1;
    }
 
    /// Like #"TString::IndexOf(TChar, integer, integer)" but in case the character is not found,
    /// this method returns the length of this string instead of \c -1.
    /// Depending on the invocation context, the choice for the right version of this method may
    /// lead to shorter and more efficient code.
    ///
    /// @param needle  The character to search for.
    /// @return This string's #".Length" if character \p{needle} is not found.
    ///         Otherwise, the index of first occurrence.
    integer      IndexOfOrLength( TChar needle )                                             const {
        ALIB_STRING_DBG_CHK(this)
        const TChar* result=   characters::Search( buffer, length, needle );
 
        return result != nullptr ? result  -  buffer
                                 : length;
    }
 
    /// Like #"TString::IndexOf(TChar, integer)" but in case the character is not found, this
    /// method returns the length of this string instead of \c -1.
    /// Depending on the invocation context, the choice for the right version of this method may
    /// lead to shorter and more efficient code.
    ///
    /// @tparam TCheck   Defaults to #"CHK;2", which is the normal invocation mode.
    ///                  If \c false is given, no range check is performed.
    /// @param needle    The character to search for.
    /// @param startIdx  The index in this to start searching the character.
    /// @return This string's #".Length" if character \p{needle} is not found.
    ///         Otherwise the index of first occurrence.
    template <typename TCheck= CHK>
    integer      IndexOfOrLength( TChar needle, integer startIdx )                           const {
        ALIB_STRING_DBG_CHK(this)
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
                 if ( startIdx <  0      )  startIdx= 0;
            else if ( startIdx >= length )  return length;
        } else {
            ALIB_ASSERT_ERROR( startIdx >= 0 && startIdx < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startIdx, length )
        }
 
        const TChar* result= characters::Search( buffer + startIdx, length - startIdx, needle );
        return result != nullptr ? result  -  buffer
                                 : length;
    }
 
    /// Searches a character starting backwards from the end or a given start index.
    ///
    /// @tparam TCheck      Defaults to #"CHK;2", which is the normal invocation mode.
    ///                     If \c false is given, no range check is performed.
    ///                     Consequently, in this case, optional parameter startIndex must be
    ///                     provided.
    ///
    /// @param needle       The character to search for.
    /// @param startIndex   The index within this string to start searching the character.
    ///                     Defaults to #"str MAX_LEN".
    ///
    /// @return \c -1 if the character \p{needle} is not found.
    ///         Otherwise, the index of its last occurrence.
    template <typename TCheck= CHK>
    integer    LastIndexOf( TChar needle, integer startIndex =MAX_LEN )                      const {
        ALIB_STRING_DBG_CHK(this)
 
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
            if ( startIndex <  0      )   return -1;
            if ( startIndex >= length )   startIndex= length-1;
        } else {
            ALIB_ASSERT_ERROR( startIndex >= 0 && startIndex < length, "STRINGS",
                "Non checking and index out of range: 0 <= {} < {}.", startIndex, length )
        }
 
        while( startIndex >= 0 && buffer[ startIndex ] != needle )
            --startIndex;
 
        return startIndex;
    }
 
    /// Returns the index of the first character which is included, respectively <em>not</em>
    /// included in a set of characters given as a
    /// #"alib_strings_cc_construction_string;string-like object".
    ///
    /// \note
    ///   In derived class #"%CString", a faster version of this method (using \c std::strpbrk()
    ///   respectively \c std::strspn()) is available.
    ///   So, if performance is important and repetitive calls are performed, it might be
    ///   advisable to hold this string and the needles in a zero-terminated string buffer,
    ///   for example, in an #"%AString".
    ///
    /// This method searches forwards. For backwards search, see #".LastIndexOf".
    ///
    /// @tparam TInclusion Denotes whether the search returns the first index that holds a value
    ///                    that is included or that is not excluded in the set of needle
    ///                    characters.
    /// @tparam TCheck     Defaults to #"CHK;2", which is the normal invocation mode.
    ///                    If \c <false> is given, no parameter checks are performed.
    /// @param needles     Pointer to a zero-terminated set of characters to be taken into
    ///                    account.
    /// @param startIdx    The index to start the search at. If the given value is less than 0,
    ///                    it is set to 0. If it exceeds the length of the string, the length of
    ///                    the string is returned.
    ///                    Defaults to 0.
    ///
    /// @return The index of the first character found which is included, respectively not
    ///         included, in the given set of characters.
    ///         If nothing is found, -1 is returned.
    template <lang::Inclusion   TInclusion,
              typename          TCheck      = CHK>
    integer    IndexOfAny( const TString& needles, integer startIdx= 0 )                     const {
        if constexpr ( TCheck::value ) {
            if ( startIdx < 0       ) startIdx= 0;
            if ( startIdx >= length ) return   -1;
        } else {
            ALIB_ASSERT_ERROR( startIdx >= 0 && startIdx < length && needles.Length() != 0,
                "STRINGS", "Non checking and illegal parameters: 0 <= {} < {}. Needles: {}",
                           startIdx, length, needles.Length() )
        }
 
 
        integer idx= TInclusion == lang::Inclusion::Include
          ? characters::IndexOfAnyIncluded( buffer + startIdx,  length - startIdx, needles.Buffer(), needles.Length() )
          : characters::IndexOfAnyExcluded( buffer + startIdx,  length - startIdx, needles.Buffer(), needles.Length() );
 
        return idx == -1 ? -1 : startIdx + idx;
    }
 
    /// Returns the index of the last character which is included, respectively <em>not</em>
    /// included in set of characters given as a
    /// #"alib_strings_cc_construction_string;string-like object".
    ///
    /// This method searches backwards starting at the given index. For forwards search, see
    /// #".IndexOfAny".
    ///
    /// @tparam TInclusion Denotes whether the search returns the first index that holds a value
    ///                    that is included or that is not excluded in the set of needle
    ///                    characters.
    /// @tparam TCheck     Defaults to #"CHK;2", which is the normal invocation mode.
    ///                    If \c <false> is given, no parameter checks are performed.
    /// @param needles     Pointer to a zero-terminated set of characters to be searched for.
    /// @param startIdx    The index to start the search at. The value is cropped to be in
    ///                    the bounds of 0 and the length of this object minus one.
    ///                    Defaults to #"str MAX_LEN".
    ///
    /// @return The index of the first character found which is included, respectively not
    ///         included, in the given set of characters.
    ///         If nothing is found, -1 is returned.
    template <lang::Inclusion TInclusion,
              typename        TCheck = CHK>
    integer LastIndexOfAny( const TString& needles, integer startIdx =MAX_LEN )              const {
        if constexpr ( TCheck::value ) {
            if ( startIdx < 0       ) return -1;
            if ( startIdx >= length ) startIdx=  length - 1;
        } else {
            ALIB_ASSERT_ERROR( startIdx >= 0 && startIdx < length && needles.Length() != 0,
                "STRINGS", "Non checking and illegal parameters: 0 <= {} < {}. Needles: {}",
                           startIdx, length, needles.Length() )
        }
 
        if constexpr ( TInclusion == lang::Inclusion::Include )
            return characters::LastIndexOfAnyInclude(  Buffer(), startIdx, needles.Buffer(), needles.Length() );
        else
            return characters::LastIndexOfAnyExclude(  Buffer(), startIdx, needles.Buffer(), needles.Length() );
    }
 
    /// Searches the given #"alib_strings_cc_construction_string;string-like object"
    /// in this string.
    ///
    /// If \p{needle} is empty, the adjusted value of \p{startIdx} is returned.
    ///
    /// @tparam TSensitivity   Case sensitivity of the comparison.
    ///                        Optional and defaults to #"%Case::Sensitive".
    /// @tparam TCheck         Defaults to #"CHK;2", which is the normal invocation mode.
    ///                        If \c false is given, parameter \p{needle} must not be empty and
    ///                        \p{startIdx} must be in the range of
    ///                        <c>[0 ...</c> #".Length" <c> - needle.Length()]</c>.
    ///                        This also implies that this string must not be empty.
    /// @param needle          The string to search for.
    /// @param startIdx        The index to start the search at. Optional and defaults to \c 0.
    /// @param endIdx          The index where the search ends. Precisely, the index of the
    ///                        first character that is not found.
    ///                        Defaults to #"str MAX_LEN".
    ///
    /// @return    If the checking of parameters failed or the string is not found, \c -1 is
    ///            returned. Otherwise the index of the first occurrence of \p{needle}.
    template<typename   TCheck        = CHK,
             lang::Case TSensitivity  = lang::Case::Sensitive>
    integer  IndexOf( const TString&  needle,
                      integer         startIdx= 0,
                      integer         endIdx  = strings::MAX_LEN  )                          const {
        if constexpr ( TCheck::value ) {
            if ( needle.IsNull()  )
                return  -1;
            if ( startIdx < 0                        )    startIdx= 0;
            endIdx= (std::min) (endIdx, length - needle.Length() + 1 );
            if ( startIdx >= endIdx                  )    return -1;
        } else {
            // this default parameter is still corrected. Optimized out anyhow.
            if( endIdx  == strings::MAX_LEN)
                endIdx= length - needle.Length() + 1;
 
            ALIB_ASSERT_ERROR(    startIdx >= 0 && startIdx <= length
                               &&                    endIdx <= length
                               && needle.IsNotNull(),
                "STRINGS", "Non checking and illegal parameters: 0 <= {} <= {}, {} <= {}. Needles: {}",
                           startIdx, length, endIdx, length, needle.Length() )
        }
 
 
        return indexOfString<TSensitivity>(needle, startIdx, endIdx);
    }
 
    /// Searches the first difference of a substring of this string and a
    /// #"alib_strings_cc_construction_string;string-like object" given with parameter
    /// \p{needle}.
    /// If no difference is found, then the index of the first character behind the substring
    /// is returned.
    ///
    /// @tparam TCheck      Defaults to #"CHK;2", which is the normal invocation mode.
    ///                     If \c false is given, no range check is performed.
    /// @param needle       The substring to search for.
    /// @param sensitivity  Letter case sensitivity of the comparison.
    ///                     Optional and defaults to #"%Case::Sensitive".
    /// @param startIdx     The index in this string to start the comparison with \p{needle}.
    ///                     Optional and defaults to \c 0.
    ///
    /// @return The index of the first difference found or \p{idx} plus the length of \p{needle}.
    template <typename TCheck= CHK>
    integer  IndexOfFirstDifference( const TString&  needle,
                                     lang::Case      sensitivity = lang::Case::Sensitive,
                                     integer         startIdx    = 0                     )   const {
        ALIB_STRING_DBG_CHK(this)
 
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
                 if ( startIdx <  0      )  startIdx= 0;
            else if ( startIdx >= length )  return startIdx;
        } else {
            ALIB_ASSERT_ERROR( startIdx >= 0 && startIdx < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startIdx, length )
        }
 
        return   characters::IndexOfFirstDifference( buffer + startIdx, length - startIdx,
                                                     needle.buffer    ,  needle.length,
                                                     sensitivity                       );
    }
 
    /// The method searches the next matching \p{closer}-character while taking nested pairs of
    /// \p{opener} and \p{closer} characters into account.
    ///
    /// Before the invocation of this method, the initial \p{opener} has to be known already,
    /// and the given \p{idx} has to point to the first character behind the opener, where the
    /// search for an according \p{closer} is to be started.
    ///
    /// This method is useful to scan a string for pairs of opening and closing brackets, while
    /// the found segment may contain nested pairs of the same brackets.
    ///
    /// @param opener The character that represents the opening bracket, e.g., <c>'{'</c>.
    /// @param closer The character that represents the closing bracket, e.g., <c>'}'</c>.
    /// @param idx    Index pointing to the first character behind the (first) \p{opener}.
    ///
    /// @return   The index of the corresponding closing character. If none was found, a negative
    ///           value is returned.
    ///           In the latter case the negated (absolute) value is indicating the number of
    ///           still open (nested) brackets.
    integer  IndexOfSegmentEnd( TChar opener, TChar closer, integer idx )                     const;
 
 
    /// Counts all occurrences of character \p{needle} in the range from \p{startPos} to the end
    /// of the string.
    ///
    /// For empty strings \p{needle}, \c 0 is returned.
    ///
    /// @tparam TCheck   Defaults to #"CHK;2", which is the normal invocation mode.
    ///                  If \c false is given, no range check is performed.
    /// @param needle    The character to search for.
    /// @param startPos  The index to start the counting.
    ///                  Optional and defaults to \c 0.
    ///
    /// @return The index of the first difference in \p{needle}.
    template <typename TCheck= CHK>
    integer  CountChar( TChar           needle,
                        integer         startPos        = 0   )                              const {
        ALIB_STRING_DBG_CHK(this)
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
                 if ( startPos <  0      )  startPos= 0;
            else if ( startPos >= length )  return 0;
        } else {
            ALIB_ASSERT_ERROR( startPos >= 0 && startPos < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startPos, length )
        }
 
 
        int     result= 0;
        while( startPos < length && (startPos= IndexOf<NC>( needle, startPos )) >= 0 ) {
            ++startPos;
            ++result;
        }
 
        return result;
    }
 
    /// Counts all occurrences of character \p{needle}, unless followed by character \p{omit}
    /// in the range from \p{startPos} to the end of the string.
    ///
    /// For empty strings \p{needle}, \c 0 is returned.
    /// Also, for empty strings \p{omit}, \c 0 is returned.
    ///
    /// @tparam TCheck   Defaults to #"CHK;2", which is the normal invocation mode.
    ///                  If \c false is given, no range check is performed.
    /// @param needle    The character to search for.
    /// @param omit      Omit occurrence if the given character follows.
    /// @param startPos  The index to start the counting.
    ///
    /// @return The index of the first difference in \p{needle}.
    template <typename TCheck= CHK>
    integer  CountChar( TChar           needle,
                        TChar           omit,
                        integer         startPos  )                                          const {
        ALIB_STRING_DBG_CHK(this)
        if constexpr ( TCheck::value ) {
            // adjust range, if empty return -1
                 if ( startPos <  0      )  startPos= 0;
            else if ( startPos >= length )  return 0;
        } else {
            ALIB_ASSERT_ERROR( startPos >= 0 && startPos < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startPos, length )
        }
 
        int     result= 0;
        while( startPos < length && (startPos= IndexOf<NC>( needle, startPos )) >= 0 ) {
            ++startPos;
            if( startPos < Length()  &&  *(buffer + startPos) == omit  )
                continue;
 
            ++result;
        }
 
        return result;
    }
 
    /// Counts all occurrences of \p{needle} from \p{startPos} to the end of the string.
    ///
    /// For empty strings \p{needle}, \c 0 is returned.
    ///
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If \c false is given, parameter \p{startIdx} must be valid and
    ///                      \p{needle} must not be empty.
    /// @tparam TSensitivity Case sensitivity of the comparison.
    ///                      Optional and defaults to #"%Case::Sensitive".
    /// @param needle        The string to search for.
    /// @param startPos      The index to start the counting.
    ///                      Optional and defaults to \c 0.
    ///
    /// @return The index of the first difference in \p{needle}.
    template< typename    TCheck       = CHK,
              lang::Case  TSensitivity = lang::Case::Sensitive >
    integer Count( const TString&    needle,
                   integer           startPos   = 0 )                                        const {
        ALIB_STRING_DBG_CHK(this)
        integer nLen= needle.Length();
        if( nLen == 0  )
            return 0;
        if constexpr ( TCheck::value ) {
            if ( startPos < 0 )                startPos= 0;
            if ( startPos + nLen > length )    return  0;
        } else {
            ALIB_ASSERT_ERROR( startPos >= 0 && startPos < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startPos, length )
        }
 
        int     result= 0;
        while( (startPos= IndexOf<NC, TSensitivity>( needle, startPos )) >= 0 ) {
            startPos+= needle.Length();
            ++result;
        }
 
        return result;
    }
 
    /// Counts all occurrences of \p{needle}, unless followed by \p{omit}, starting at
    /// \p{startPos} to the end of the string.
    ///
    /// For empty strings \p{needle}, \c 0 is returned.
    /// Also, for empty strings \p{omit}, \c 0 is returned.
    ///
    /// @tparam TSensitivity Case sensitivity of the comparison.
    ///                      Optional and defaults to #"%Case::Sensitive".
    /// @tparam TCheck       Defaults to #"CHK;2", which is the normal invocation mode.
    ///                      If \c false is given, parameter \p{startPos} must be valid and
    ///                      \p{needle} must not be empty.
    /// @param needle        The string to search for.
    /// @param omit          Omit occurrence if the given string follows.
    /// @param startPos      The index to start the counting.
    ///                      Optional and defaults to \c 0.
    ///
    /// @return The index of the first difference in \p{needle}.
    template<typename    TCheck        = CHK,
             lang::Case  TSensitivity  = lang::Case::Sensitive>
    integer  Count( const TString&   needle,
                    const TString&   omit,
                    integer          startPos        = 0         )                           const {
        ALIB_STRING_DBG_CHK(this)
        integer nLen= needle.Length();
        if ( nLen == 0  )
            return  0;
        if constexpr ( TCheck::value ) {
            if ( startPos < 0 )                startPos= 0;
            if ( startPos + nLen > length )    return  0;
        } else {
            ALIB_ASSERT_ERROR( startPos >= 0 && startPos < length, "STRINGS",
                           "Non checking and index out of range: 0 <= {} < {}.", startPos, length )
        }
 
 
        int     result= 0;
        while( (startPos= IndexOf<NC , TSensitivity>( needle, startPos )) >= 0 ) {
            startPos+= nLen;
            if(    startPos + omit.Length() <= Length()
                && (    omit.IsEmpty()
                     || ContainsAt<NC>( omit, startPos ) )    )
                continue;
 
            ++result;
        }
 
        return result;
    }
 
  //################################################################################################
  //  Parsing Numbers
  //################################################################################################
 
    /// Parses an integral value consisting of characters \c '0' to \c '9' from this string.
    /// <br>Unlike with #".ParseInt(integer, TNumberFormat<TChar>*)" or
    /// #".ParseDec(integer, TNumberFormat<TChar>*)", no sign, whitespaces, or group characters are
    /// accepted.
    ///
    /// @param startIdx     The start index from where the integral value is tried to be parsed.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first character
    ///                     in this string after the float number that was parsed.
    ///                     If parsing fails, it will be set to the value of parameter startIdx.
    ///                     Therefore, this parameter can be used to check if a value was found.
    ///
    /// @return The parsed value. In addition, the parameter \p{newIdx} is set to point
    ///         to the first character behind any found integer number.
    ALIB_DLL
    uint64_t  ParseDecDigits( integer startIdx =0, integer* newIdx= nullptr )                 const;
 
 
    /// Parses an integral value in decimal, binary, hexadecimal or octal format from
    /// the string
    ///
    /// Parameter \p{numberFormat} defaults to \c nullptr. This denotes static singleton
    /// #"TNumberFormat::Computational;NumberFormat::Computational"
    /// which is configured to not using - and therefore also not parsing - grouping characters.
    ///
    /// Optional output parameter \p{newIdx} may be used to detect if parsing was successful.
    /// If not, it receives the value of \p{startIdx}, even if leading whitespaces had been
    /// read.
    ///
    /// For more information on number conversion, see class
    /// #"TNumberFormat;NumberFormat". All of its interface methods
    /// have a corresponding implementation within class #"%AString".
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    ALIB_DLL
    int64_t  ParseInt( integer startIdx =0, TNumberFormat<TChar>* numberFormat= nullptr,
                       integer* newIdx= nullptr )                                             const;
 
    /// Overloaded version of #"TString::ParseInt(integer, TNumberFormat<TChar>*, integer*)"
    /// providing default values for omitted parameters.
    ///
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    int64_t  ParseInt( TNumberFormat<TChar>* numberFormat, integer* newIdx= nullptr )          const
    { return ParseInt( 0, numberFormat, newIdx ); }
 
    /// Overloaded version of #"TString::ParseInt(integer, TNumberFormat<TChar>*, integer*)"
    /// providing default values for omitted parameters.
    ///
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    int64_t  ParseInt( integer* newIdx )            const { return ParseInt( 0, nullptr, newIdx ); }
 
 
    /// Overloaded version of #"TString::ParseInt(integer, TNumberFormat<TChar>*, integer*)"
    /// providing default values for omitted parameters.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    int64_t  ParseInt( integer startIdx, integer* newIdx )                                     const
    { return ParseInt( startIdx, nullptr, newIdx ); }
 
    /// Reads an unsigned 64-bit integer in standard decimal format at the given position
    /// from this #"%AString".
    ///
    /// Parameter \p{numberFormat} defaults to \c nullptr. This denotes static singleton
    /// #"str TNumberFormat::Computational"
    /// which is configured to not using - and therefore also not parsing - grouping characters.
    ///
    /// Optional output parameter \p{newIdx} may be used to detect if parsing was successful.
    /// If not, it receives the value of \p{startIdx}, even if leading whitespaces had been
    /// read.
    ///
    /// Sign literals \c '-' or \c '+' are \b not accepted and parsing will fail.
    /// For reading signed integral values, see methods #ParseInt, for floating point numbers
    /// #ParseFloat.
    ///
    /// For more information on number conversion, see class
    /// #"TNumberFormat;NumberFormat". All number-parsing interface methods
    /// have a corresponding implementation within this class.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    ALIB_DLL
    uint64_t  ParseDec( integer startIdx =0, TNumberFormat<TChar>* numberFormat= nullptr,
                        integer* newIdx= nullptr )                                            const;
 
    /// Overloaded version of
    /// #"TString::ParseDec(integer,TNumberFormat<TChar>*,integer*)const;ParseDec"
    /// providing default values for omitted parameters.
    ///
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseDec( TNumberFormat<TChar>* numberFormat, integer* newIdx= nullptr )         const
    { return ParseDec( 0, numberFormat, newIdx ); }
 
    /// Overloaded version of
    /// #"TString::ParseDec(integer,TNumberFormat<TChar>*,integer*)const;ParseDec"
    /// providing default values for omitted parameters.
    ///
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseDec( integer* newIdx )           const { return ParseDec( 0, nullptr, newIdx ); }
 
 
    /// Overloaded version of
    /// #"TString::ParseDec(integer,TNumberFormat<TChar>*,integer*)const;ParseDec"
    /// providing default values for omitted parameters.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseDec( integer startIdx, integer* newIdx )                                    const
    { return ParseDec( startIdx, nullptr, newIdx ); }
 
    /// Reads an unsigned 64-bit integer in binary format at the given position
    /// from this string.
    ///
    /// Parameter \p{numberFormat} defaults to \c nullptr. This denotes static singleton
    /// #"TNumberFormat::Computational;NumberFormat::Computational"
    /// which is configured to not using - and therefore also not parsing - grouping characters.
    ///
    /// Optional output parameter \p{newIdx} may be used to detect if parsing was successful.
    /// If not, it receives the value of \p{startIdx}, even if leading whitespaces had been
    /// read.
    ///
    /// For more information on number conversion, see class
    /// #"TNumberFormat;NumberFormat". All number-parsing interface methods
    /// have a corresponding implementation within this class.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    ALIB_DLL
    uint64_t  ParseBin( integer startIdx =0, TNumberFormat<TChar>* numberFormat= nullptr,
                        integer* newIdx= nullptr )                                            const;
 
 
    /// Overloaded version of
    /// #"TString::ParseBin(integer,TNumberFormat<TChar>*,integer*)const;ParseBin"
    /// providing default values for omitted parameters.
    ///
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseBin( TNumberFormat<TChar>* numberFormat, integer* newIdx= nullptr )         const
    { return ParseBin( 0, numberFormat, newIdx ); }
 
    /// Overloaded version of
    /// #"TString::ParseBin(integer,TNumberFormat<TChar>*,integer*)const;ParseBin"
    /// providing default values for omitted parameters.
    ///
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseBin( integer* newIdx )           const { return ParseBin( 0, nullptr, newIdx ); }
 
 
    /// Overloaded version of
    /// #"TString::ParseBin(integer,TNumberFormat<TChar>*,integer*)const;ParseBin"
    /// providing default values for omitted parameters.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseBin( integer startIdx, integer* newIdx )                                    const
    { return ParseBin( startIdx, nullptr, newIdx ); }
 
    /// Reads an unsigned 64-bit integer in hexadecimal format at the given position
    /// from this string.
    ///
    /// Parameter \p{numberFormat} defaults to \c nullptr. This denotes static singleton
    /// #"TNumberFormat::Computational;NumberFormat::Computational"
    /// which is configured to not using - and therefore also not parsing - grouping characters.
    ///
    /// Optional output parameter \p{newIdx} may be used to detect if parsing was successful.
    /// If not, it receives the value of \p{startIdx}, even if leading whitespaces had been
    /// read.
    ///
    /// For more information on number conversion, see class
    /// #"TNumberFormat;NumberFormat". All number-parsing interface methods
    /// have a corresponding implementation within this class.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    ALIB_DLL
    uint64_t  ParseHex( integer startIdx =0, TNumberFormat<TChar>* numberFormat= nullptr,
                        integer* newIdx= nullptr )                                            const;
 
 
    /// Overloaded version of
    /// #"TString::ParseHex(integer,TNumberFormat<TChar>*,integer*)const;ParseHex"
    /// providing default values for omitted parameters.
    ///
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseHex( TNumberFormat<TChar>* numberFormat, integer* newIdx= nullptr )         const
    { return ParseHex( 0, numberFormat, newIdx ); }
 
    /// Overloaded version of
    /// #"TString::ParseHex(integer,TNumberFormat<TChar>*,integer*)const;ParseHex"
    /// providing default values for omitted parameters.
    ///
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseHex( integer* newIdx )           const { return ParseHex( 0, nullptr, newIdx ); }
 
 
    /// Overloaded version of
    /// #"TString::ParseHex(integer,TNumberFormat<TChar>*,integer*)const;ParseHex"
    /// providing default values for omitted parameters.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseHex( integer startIdx, integer* newIdx )                                    const
    { return ParseHex( startIdx, nullptr, newIdx ); }
 
    /// Reads an unsigned 64-bit integer in octal format at the given position
    /// from this string.
    ///
    /// Parameter \p{numberFormat} defaults to \c nullptr. This denotes static singleton
    /// #"TNumberFormat::Computational;NumberFormat::Computational"
    /// which is configured to not using - and therefore also not parsing - grouping characters.
    ///
    /// Optional output parameter \p{newIdx} may be used to detect if parsing was successful.
    /// If not, it receives the value of \p{startIdx}, even if leading whitespaces had been
    /// read.
    ///
    /// For more information on number conversion, see class
    /// #"TNumberFormat;NumberFormat". All number-parsing interface methods
    /// have a corresponding implementation within this class.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    ALIB_DLL
    uint64_t  ParseOct( integer startIdx =0, TNumberFormat<TChar>* numberFormat= nullptr,
                        integer* newIdx= nullptr )                                            const;
 
 
    /// Overloaded version of
    /// #"TString::ParseOct(integer,TNumberFormat<TChar>*,integer*)const;ParseOct"
    /// providing default values for omitted parameters.
    ///
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseOct( TNumberFormat<TChar>* numberFormat, integer* newIdx= nullptr )         const
    { return ParseOct( 0, numberFormat, newIdx ); }
 
    /// Overloaded version of
    /// #"TString::ParseOct(integer,TNumberFormat<TChar>*,integer*)const;ParseOct"
    /// providing default values for omitted parameters.
    ///
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseOct( integer* newIdx )           const { return ParseOct( 0, nullptr, newIdx ); }
 
 
    /// Overloaded version of
    /// #"TString::ParseOct(integer,TNumberFormat<TChar>*,integer*)const;ParseOct"
    /// providing default values for omitted parameters.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    uint64_t  ParseOct( integer startIdx, integer* newIdx )                                    const
    { return ParseOct( startIdx, nullptr, newIdx ); }
 
    /// Reads a floating point number at the given position from this string.
    ///
    /// Parameter \p{numberFormat} defaults to \c nullptr. This denotes static singleton
    /// #"TNumberFormat::Computational;NumberFormat::Computational"
    /// which is configured to 'international' settings (not using the locale) and therefore
    /// also not parsing grouping characters.
    ///
    /// Optional output parameter \p{newIdx} may be used to detect if parsing was successful.
    /// If not, it receives the value of \p{startIdx}, even if leading whitespaces had been
    /// read.
    ///
    /// For more information on number conversion, see class
    /// #"TNumberFormat;NumberFormat". All number-parsing interface methods
    /// have a corresponding implementation within this class.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    ALIB_DLL
    double   ParseFloat( integer startIdx =0, TNumberFormat<TChar>* numberFormat= nullptr,
                         integer* newIdx= nullptr )                                           const;
 
    /// Overloaded version of
    /// #"TString::ParseFloat(integer,TNumberFormat<TChar>*,integer*)const;ParseFloat"
    /// providing default values for omitted parameters.
    ///
    /// @param numberFormat The format definition. Defaults to \c nullptr.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    double  ParseFloat( TNumberFormat<TChar>* numberFormat, integer* newIdx= nullptr )         const
    { return ParseFloat( 0, numberFormat, newIdx ); }
 
    /// Overloaded version of
    /// #"TString::ParseFloat(integer,TNumberFormat<TChar>*,integer*)const;ParseFloat"
    /// providing default values for omitted parameters.
    ///
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \c 0.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    double  ParseFloat( integer* newIdx )         const { return ParseFloat( 0, nullptr, newIdx ); }
 
 
    /// Overloaded version of
    /// #"TString::ParseFloat(integer,TNumberFormat<TChar>*,integer*)const;ParseFloat"
    /// providing default values for omitted parameters.
    ///
    /// @param startIdx     The start index for parsing.
    ///                     Optional and defaults to \c 0.
    /// @param[out] newIdx  Optional output variable that will point to the first
    ///                     character in this string after the number parsed.
    ///                     On failure, it will be set to the initial value \p{startIdx}.
    /// @return The parsed value. In addition, the output parameter \p{newIdx} is set to
    ///         point to the first character behind the parsed number.
    double  ParseFloat( integer startIdx, integer* newIdx )                                    const
    { return ParseFloat( startIdx, nullptr, newIdx ); }
 
  //################################################################################################
  //  Conversion
  //################################################################################################
 
    /// Copies this string's contents into a given character buffer.
    /// It is the caller's responsibility that \p{dest} is large enough, write-enabled, etc.
    ///
    /// @param dest   The destination buffer.
    /// @return    The length of this string.
    integer CopyTo( TChar* dest )                                                            const {
        if (IsNotEmpty())
            characters::Copy( buffer, length, dest );
        return length;
    }
 
    /// Sets this String to a copy of the given string, allocated in given \p{allocator}.
    ///
    /// \note
    ///   In case the given \p{copy} is empty or nulled, no allocation is performed and this
    ///   string is set to empty. Still, the pointer to the buffer is copied.
    ///   Thus, this string behaves in respect to the method #IsNull the same as the given
    ///   string \p{copy}.
    ///
    /// @tparam TAllocator The type of the given \p{allocator}, as prototyped with class
    ///                    #"lang::Allocator". Deduced by the compiler.
    /// @param  allocator  The allocator to use.
    /// @param  copy       The string to copy to the new memory allocated.
    template<typename TAllocator>
    requires alib::lang::IsAllocator<TAllocator>
    void  Allocate( TAllocator& allocator, const TString<TChar>& copy ) {
        if( (length= copy.length) == 0 ) {
            buffer= copy.buffer;
            return;
        }
 
        auto* newBuf=  allocator().template AllocArray<TChar>( copy.length );
        copy.CopyTo( newBuf );
        buffer= newBuf;
    }
 
    /// Deallocates this String's memory in \p{allocator} and sets this instance to \e nulled.
    /// \note
    ///   In case this instance is empty or nulled, no deallocation is performed.
    ///   This should not happen with due usage, which is:
    ///   - A string is allocated using the method #Allocate on another instance.
    ///   - For the allocated string, this method is to be called, passing the same allocator.
    ///
    /// \note
    ///   Nevertheless, because the method #Allocate likewise does not perform an allocation call
    ///   in the case an empty string was given, it is a valid use to allocate and later deallocate
    ///   empty strings.
    /// @tparam TAllocator The type of the given \p{allocator}, as prototyped with the class
    ///                    #"lang::Allocator". Deduced by the compiler.
    /// @param  allocator  The allocator to use.
    template<typename TAllocator>
    requires alib::lang::IsAllocator<TAllocator>
    void  Free( TAllocator& allocator ) {
        if( length == 0 || buffer == nullptr )
            return;
        allocator().FreeArray( buffer, length );
    }
 
  public:
  //################################################################################################
  //  Helper Methods
  //################################################################################################
 
    /// Adjusts a region given as in/out parameters, to fit to this object's range [0..length].
    ///
    /// @param[in,out] regionStart  The proposed region start which might get adjusted to fit to
    ///                             range [0..length].
    /// @param[in,out] regionLength The proposed region length which might get adjusted to fit to
    ///                             range [0..length].
    ///
    /// @return   Returns \c true, if the adjusted region is empty.
    bool AdjustRegion( integer& regionStart, integer& regionLength )                         const {
        // if start exceeds string, set to empty range at the end of the string and return true
        if (regionStart >= length) {
            regionStart=    length;
            regionLength=    0;
            return true; // indicate empty
        }
 
        // if negative start, cut it from the length
        if (regionStart < 0 ) {
            regionLength+=  regionStart;
            regionStart=    0;
        }
 
        // adjust length
        if ( regionLength < 0 ) {
            regionLength= 0;
            return true;
        }
 
        integer maxRegionLength=  length - regionStart;
        if ( regionLength > maxRegionLength )
             regionLength=  maxRegionLength;
 
        // return true if adjusted region is empty
        return  regionLength == 0;
    }
 
 
    /// Implementation of \c std::iterator_traits for class #"%TString" and its descendents.
    /// Base class #"%^String" exposes #const_iterator which uses
    /// <c>const TChar*</c> and <c>const TChar&</c> for template types \p{TPointer} and
    /// \p{TReference}. Descendant classes may expose a mutable version (e.g., #"^AString").
    ///
    /// As the name of the class indicates, this iterator satisfies the C++ standard library
    /// concept
    /// \https{RandomAccessIterator,en.cppreference.com/w/cpp/concept/RandomAccessIterator}.
    template<typename TCharConstOrMutable>
    class TRandomAccessIterator {
      public:
        using iterator_category = std::random_access_iterator_tag;  ///< Implementation of <c>std::iterator_traits</c>.
        using value_type        = TCharConstOrMutable;              ///< Implementation of <c>std::iterator_traits</c>.
        using difference_type   = integer;                          ///< Implementation of <c>std::iterator_traits</c>.
        using pointer           = TCharConstOrMutable*;             ///< Implementation of <c>std::iterator_traits</c>.
        using reference         = TCharConstOrMutable&;             ///< Implementation of <c>std::iterator_traits</c>.
 
      protected:
        /// The pointer into the buffer is all we store.
        TCharConstOrMutable* p;
      public:
        /// Constructor.
        /// @param start Pointer to the initial character.
        explicit TRandomAccessIterator( TCharConstOrMutable* start = nullptr ) : p(start)         {}
 
      //############################ To satisfy concept of  InputIterator ##########################
 
        /// Prefix increment operator.
        /// @return A reference to this object.
        TRandomAccessIterator& operator++()                                   { ++p; return *this; }
 
        /// Postfix increment operator.
        /// @return An iterator value that is not increased, yet.
        TRandomAccessIterator operator++(int)                 { return TRandomAccessIterator(p++); }
 
        /// Comparison operator.
        /// @param other  The iterator to compare ourselves to.
        /// @return \c true if this and the given iterator are pointing to the same character
        ///         in the same array, \c false otherwise.
        bool operator==(TRandomAccessIterator other)                  const { return p == other.p; }
 
        /// Comparison operator.
        /// @param other  The iterator to compare ourselves to.
        /// @return \c true if this and given iterator are not equal, \c false otherwise.
        bool operator!=(TRandomAccessIterator other)             const { return !(*this == other); }
 
        /// Retrieves the character that this iterator references.
        /// @return The character value.
        TCharConstOrMutable& operator*()                                        const { return *p; }
 
        /// Retrieves the character that this iterator references.
        /// @return The character value.
        TCharConstOrMutable& operator*()                                              { return *p; }
 
 
      //######################## To satisfy concept of  BidirectionalIterator ######################
 
        /// Prefix decrement operator.
        /// @return A reference to this object.
        TRandomAccessIterator& operator--()                                   { --p; return *this; }
 
 
        /// Postfix decrement operator.
        /// @return The iterator value prior the decrement operation.
        TRandomAccessIterator operator--(int)                 { return TRandomAccessIterator(p--); }
 
 
      //######################## To satisfy concept of  RandomAccessIterator #######################
 
        /// Addition assignment.
        /// @param n The value to subtract.
        /// @return A reference to this iterator.
        TRandomAccessIterator& operator+=(integer n)                        { p+= n; return *this; }
 
        /// Subtraction assignment.
        /// @param n The value to subtract.
        /// @return A reference to this iterator.
        TRandomAccessIterator& operator-=(integer n)                        { p-= n; return *this; }
 
        /// Addition.
        /// @param n The value to subtract.
        /// @return The resulting iterator value.
        TRandomAccessIterator operator+(integer n)  const { return TRandomAccessIterator( p + n ); }
 
        /// Subtraction.
        /// @param n The value to subtract.
        /// @return The resulting iterator value.
        TRandomAccessIterator operator-(integer n)  const { return TRandomAccessIterator( p - n ); }
 
        /// Difference (distance) from this iterator to the given one.
        /// @param other  The iterator to subtract
        /// @return The difference between (distance of) this and the given iterator.
        integer operator-(TRandomAccessIterator other)                 const { return p - other.p; }
 
        /// Subscript operator.
        /// @param n  The distance to add.
        /// @return Reference to the character referenced by this iterator plus the distance
        ///         given.
        TCharConstOrMutable& operator[]( integer n )                    const { return *( p + n ); }
 
      //#### Comparison operators (also needed to satisfy concept of RandomAccessIterator) ###
 
        /// Compares this iterator with the given one.
        /// @param other  The iterator to compare
        /// @return \c true if this iterator is \e smaller than \p{other},
        ///         \c false otherwise.
        bool operator<(TRandomAccessIterator other)                    const { return p < other.p; }
 
        /// Compares this iterator with the given one.
        /// @param other  The iterator to compare
        /// @return \c true if this iterator is \e smaller than or equal to \p{other},
        ///         \c false otherwise.
        bool operator<=(TRandomAccessIterator other)                  const { return p <= other.p; }
 
        /// Compares this iterator with the given one.
        /// @param other  The iterator to compare
        /// @return \c true if this iterator is \e greater than \p{other},
        ///         \c false otherwise.
        bool operator>(TRandomAccessIterator other)                    const { return p > other.p; }
 
        /// Compares this iterator with the given one.
        /// @param other  The iterator to compare
        /// @return \c true if this iterator is \e greater than or equal to \p{other},
        ///         \c false otherwise.
        bool operator>=(TRandomAccessIterator other)                  const { return p >= other.p; }
    };
 
  //################################################################################################
  //  Iteration (std::iterator_traits)
  //################################################################################################
  
    /// The constant iterator exposed by this character container. A Mutable version is
    /// found only in descendant classes (e.g., #"^AString").
    using const_iterator         = TRandomAccessIterator<const TChar>;
 
    /// The constant reverse iterator exposed by this character container. A Mutable version is
    /// found only in descendant classes (e.g., #"^AString").
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
    /// Returns an iterator pointing to a constant character at the start of this string.
    /// @return The start of this string.
    const_iterator          begin()              const { return const_iterator( buffer          ); }
 
    /// Returns an iterator pointing to a constant character at the start of this string.
    /// @return The start of this string.
    const_iterator         cbegin()              const { return const_iterator( buffer          ); }
 
    /// Returns an iterator pointing behind this string.
    /// @return The end of this string.
    const_iterator         end()                 const { return const_iterator( buffer + length ); }
 
    /// Returns an iterator pointing behind this string.
    /// @return The end of this string.
    const_iterator         cend()                const { return const_iterator( buffer + length ); }
 
    /// Returns a reverse iterator pointing to a constant character at the end of this string.
    /// @return The last character of this string.
    const_reverse_iterator rbegin()              const { return const_reverse_iterator( end()   ); }
 
    /// Returns a reverse iterator pointing before the start of this string.
    /// @return The character before this string.
    const_reverse_iterator rend()                const { return const_reverse_iterator( begin() ); }
 
    /// Returns a reverse iterator pointing to a constant character at the end of this string.
    /// @return The last character of this string.
    const_reverse_iterator crbegin()             const { return const_reverse_iterator( end()   ); }
 
    /// Returns a reverse iterator pointing before the start of this string.
    /// @return The character before this string.
    const_reverse_iterator crend()               const { return const_reverse_iterator( begin() ); }
 
    /// Returns #Length as \c size_t. Added for compatibility with the standard library.
    /// @return The character before this string.
    size_type              size()                                         const { return Length(); }
 
  //################################################################################################
 
    /// Constructs this string using start and end iterators.
    ///
    /// @param start An iterator referencing the start of the string.
    /// @param end   An iterator referencing the end of the string.
    TString( const_iterator& start, const_iterator& end )
    : buffer( &*start)
    , length( end-start >= 0 ? end-start : 0 )                                                    {}
 
  protected:
    #if !DOXYGEN
        ALIB_ALLOW_DOCS // needed due to a bug in current clang
    #endif
 
    /// Implementation of the substring search function.
    /// \attention This protected method expects valid (in range) parameters!
    ///            Parameter \p{endIdx} must be smaller or equal to the length of this string
    ///            minus the length of \p{needle} plus \c 1.
    /// @tparam TSensitivity The letter case sensitivity of the search.
    /// @param  needle       The substring to search.
    /// @param  startIdx     The start index of the search.
    /// @param  endIdx       The index where the search ends. Precisely, the index of the
    ///                      first character that is not found.
    /// @return The index of the first occurrence of \p{needle}, respectively \c -1 if not found.
    template<lang::Case TSensitivity =lang::Case::Sensitive>
    ALIB_DLL integer
    indexOfString( const TString&  needle, integer startIdx, integer endIdx )                 const;
 
    #if !DOXYGEN
        ALIB_POP_ALLOWANCE
    #endif
}; // class TString
 
//##################################################################################################
// Specializations of ArrayTraits for class TString
//##################################################################################################
} namespace alib::characters {
 
#if !DOXYGEN
template<typename TChar>
struct ArrayTraits<strings::TString<TChar>, TChar> {
    using T= strings::TString<TChar>;
    static constexpr Policy       Access                                    = Policy::Implicit;
    static constexpr Policy       Construction                              = Policy::Implicit;
    static constexpr const TChar* Buffer   (const T& src)                   { return src.Buffer(); }
    static constexpr integer      Length   (const T& src)                   { return src.Length(); }
    static constexpr T            Construct(const TChar* b, integer l)           { return T(b, l); }
};
 
template<typename TChar>
struct ZTArrayTraits<strings::TString<TChar>, TChar> {
    using T= strings::TString<TChar>;
    static constexpr Policy       Access                                   = Policy::ExplicitOnly;
    static constexpr Policy       Construction                             = Policy::ExplicitOnly;
    static constexpr const TChar* Buffer(const T& src)                      { return src.Buffer(); }
    static constexpr integer      Length(const T& src)                      { return src.Length(); }
    static constexpr T            Construct(const TChar* b, integer l )          { return T(b, l); }
};
#endif // !DOXYGEN
 
} namespace alib::strings {
//##################################################################################################
//  Comparison Operators
//##################################################################################################
#if DOXYGEN
 
//==================================================================================================
/// Starship operator and <c>==</c> operator for \alib Strings and compatible types.
///
/// The operators use the methods #"TString::Equals" and #"TString::CompareTo(const TString<TChar>)"
/// for evaluation.
///
/// For performance-critical sections, the original methods may be used where template
/// parameter \p{TCheck} can be set to #"NC".
///
/// \note For avoiding redundancy, only <c>operator<=></c> is listed here in the documentation.
///       Internally, different overloads with different requirements are used and, of course,
///       <b>operator==</b> is likewise given.<br>
///       Furthermore, all operators are available for the derived string types
///       #"%CString", #"%AString" and #"%^Substring" likewise.
///
/// @param  lhs         The left-hand operand of string-like type.
/// @param  rhs         The right-hand operand of string-like type.
/// @returns The result of the comparison.
//==================================================================================================
auto  operator<=>(const String& lhs, const String& rhs);
#else
 
// Note(25/01/17):
//   Clang strangely did not find the following templated operators when they resided in an
//   exported namespace.
//   The workaround was to not export the namespace but export each operator instead.
//   We think this is wrong behavior and not aligned with the language specification.
} namespace alib::strings {
 
ALIB_EXPORT
template<typename TChar>
bool operator== (const TString<TChar>& lhs, const TString<TChar>& rhs)
{ return  lhs. template Equals   <CHK, lang::Case::Sensitive>(rhs); }
 
ALIB_EXPORT
template<typename TChar, typename T>
requires (!std::is_same_v<T, TString<TChar>>)
bool operator== (const TString<TChar>& lhs, const T&     rhs)
{ return  lhs. template Equals   <CHK, lang::Case::Sensitive>(rhs); }
 
ALIB_EXPORT
template<typename TChar>
auto operator<=> (const TString<TChar>& lhs, const TString<TChar>& rhs)
{ return  lhs. template CompareTo<CHK, lang::Case::Sensitive>(rhs); }
 
ALIB_EXPORT
template<typename TChar, typename T>
requires (!std::same_as<TString<TChar>, T>)
auto operator<=> (const TString<TChar>& lhs, const T&     rhs)
{ return  lhs. template CompareTo<CHK, lang::Case::Sensitive>(rhs); }
 
} ALIB_EXPORT namespace alib::strings {
#endif // DOXYGEN
 
 
//##################################################################################################
// Template instantiation declarations
//##################################################################################################
#if !DOXYGEN
 
template<>      ALIB_DLL integer  TString<nchar>::WStringLength                       ()      const;
extern template ALIB_DLL integer  TString<nchar>::indexOfString<lang::Case::Sensitive>( const TString<nchar >&, integer, integer ) const;
extern template ALIB_DLL integer  TString<nchar>::indexOfString<lang::Case::Ignore   >( const TString<nchar >&, integer, integer ) const;
extern template ALIB_DLL integer  TString<nchar>::IndexOfSegmentEnd                   ( nchar, nchar, integer                    ) const;
extern template ALIB_DLL uint64_t TString<nchar>::ParseDecDigits                      ( integer, integer*                        ) const;
extern template ALIB_DLL  int64_t TString<nchar>::ParseInt                            ( integer, TNumberFormat<nchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<nchar>::ParseDec                            ( integer, TNumberFormat<nchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<nchar>::ParseBin                            ( integer, TNumberFormat<nchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<nchar>::ParseHex                            ( integer, TNumberFormat<nchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<nchar>::ParseOct                            ( integer, TNumberFormat<nchar>*, integer* ) const;
extern template ALIB_DLL double   TString<nchar>::ParseFloat                          ( integer, TNumberFormat<nchar>*, integer* ) const;
extern template ALIB_DLL size_t   TString<nchar>::Hashcode                            ()                                           const;
extern template ALIB_DLL size_t   TString<nchar>::HashcodeIgnoreCase                  ()                                           const;
 
template<> inline        integer  TString<wchar>::WStringLength                       () const { return length; }
extern template ALIB_DLL integer  TString<wchar>::indexOfString<lang::Case::Sensitive>(const TString<wchar>&, integer, integer   ) const;
extern template ALIB_DLL integer  TString<wchar>::indexOfString<lang::Case::Ignore   >(const TString<wchar>&, integer, integer   ) const;
extern template ALIB_DLL integer  TString<wchar>::IndexOfSegmentEnd                   (wchar, wchar, integer                     ) const;
extern template ALIB_DLL uint64_t TString<wchar>::ParseDecDigits                      ( integer, integer*                        ) const;
extern template ALIB_DLL  int64_t TString<wchar>::ParseInt                            ( integer, TNumberFormat<wchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<wchar>::ParseDec                            ( integer, TNumberFormat<wchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<wchar>::ParseBin                            ( integer, TNumberFormat<wchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<wchar>::ParseHex                            ( integer, TNumberFormat<wchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<wchar>::ParseOct                            ( integer, TNumberFormat<wchar>*, integer* ) const;
extern template ALIB_DLL double   TString<wchar>::ParseFloat                          ( integer, TNumberFormat<wchar>*, integer* ) const;
extern template ALIB_DLL size_t   TString<wchar>::Hashcode                            ()                                           const;
extern template ALIB_DLL size_t   TString<wchar>::HashcodeIgnoreCase                  ()                                           const;
 
template<>      ALIB_DLL integer  TString<xchar>::WStringLength                       ()      const;
extern template ALIB_DLL integer  TString<xchar>::indexOfString<lang::Case::Sensitive>( const TString<xchar >&, integer, integer ) const;
extern template ALIB_DLL integer  TString<xchar>::indexOfString<lang::Case::Ignore   >( const TString<xchar >&, integer, integer ) const;
extern template ALIB_DLL integer  TString<xchar>::IndexOfSegmentEnd                   ( xchar, xchar, integer                    ) const;
extern template ALIB_DLL uint64_t TString<xchar>::ParseDecDigits                      ( integer, integer*                        ) const;
extern template ALIB_DLL  int64_t TString<xchar>::ParseInt                            ( integer, TNumberFormat<xchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<xchar>::ParseDec                            ( integer, TNumberFormat<xchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<xchar>::ParseBin                            ( integer, TNumberFormat<xchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<xchar>::ParseHex                            ( integer, TNumberFormat<xchar>*, integer* ) const;
extern template ALIB_DLL uint64_t TString<xchar>::ParseOct                            ( integer, TNumberFormat<xchar>*, integer* ) const;
extern template ALIB_DLL double   TString<xchar>::ParseFloat                          ( integer, TNumberFormat<xchar>*, integer* ) const;
extern template ALIB_DLL size_t   TString<xchar>::Hashcode                            ()                                           const;
extern template ALIB_DLL size_t   TString<xchar>::HashcodeIgnoreCase                  ()                                           const;
 
//##################################################################################################
// debug members
//##################################################################################################
#if ALIB_DEBUG_STRINGS
    extern template ALIB_DLL void    TString<nchar>::dbgCheck() const;
    extern template ALIB_DLL void    TString<wchar>::dbgCheck() const;
    extern template ALIB_DLL void    TString<xchar>::dbgCheck() const;
#endif
 
#endif //!DOXYGEN
 
//##################################################################################################
// TString aliases
//##################################################################################################
} ALIB_EXPORT namespace alib {
 
/// Type alias in namespace #"%alib".
using  String           =     strings::TString    <character>;
 
/// Type alias in namespace #"%alib".
using  ComplementString =     strings::TString    <complementChar>;
 
/// Type alias in namespace #"%alib".
using  StrangeString    =     strings::TString    <strangeChar>;
 
/// Type alias in namespace #"%alib".
using  NString          =     strings::TString    <nchar>;
 
/// Type alias in namespace #"%alib".
using  WString          =     strings::TString    <wchar>;
 
/// Type alias in namespace #"%alib".
using  XString          =     strings::TString    <xchar>;
}
//##################################################################################################
// TString Constants
//##################################################################################################
namespace alib::strings {
#if DOXYGEN
//==================================================================================================
/// This template class has three specializations for types #"characters::nchar",
/// #"characters::wchar", and #"characters::xchar", which each provides the static method
/// #EmptyString.
/// (The only non-zero-terminated string-constant needed/supported by \alib.)
///
/// The class is useful to implement methods that are templated with the character type they use
/// and that are in need of an empty string instance.
///
/// In non-templated code (that works with fixed or logical character sizes), the following
/// \c constexpr namespace constants are rather to be used:
/// #"EMPTY_STRING", #"EMPTY_COMPLEMENT_STRING", #"EMPTY_STRANGE_STRING",
/// #"EMPTY_NSTRING", #"EMPTY_WSTRING", and #"EMPTY_XSTRING".
///
/// Nulled strings are not defined here, as they any time can be constructed using \c nullptr.
/// To improve readability, \c constexpr namespace variable are given with #"NULL_STRING",
/// #"NULL_COMPLEMENT_STRING", #"NULL_STRANGE_STRING", #"NULL_NSTRING",
/// #"NULL_WSTRING", and #"NULL_XSTRING".
///
/// @see
///   Manual chapter #"alib_strings_details_constants".
///
/// @tparam TChar The #"alib_characters_chars;character type".
//==================================================================================================
template<typename TChar> struct StringConstantsTraits {
    ///@return An empty string.
    constexpr static String<TChar>     EmptyString();
};
#else // DOXYGEN
template<typename TChar> struct StringConstantsTraits {};
template<> struct StringConstantsTraits<nchar> { constexpr static NString EmptyString() { return         "" ; } };
template<> struct StringConstantsTraits<wchar> { constexpr static WString EmptyString() { return A_WCHAR(""); } };
template<> struct StringConstantsTraits<xchar> { constexpr static XString EmptyString() { return A_XCHAR(""); } };
#endif  //!DOXYGEN
 
} // namespace [alib::strings]
 
ALIB_EXPORT namespace alib {
 
/// An empty string of the default character type.
inline constexpr const String      EMPTY_STRING          = strings::StringConstantsTraits<character     >::EmptyString();
 
/// An empty string of the complement character type.
inline constexpr ComplementString  EMPTY_COMPLEMENT_STRING= strings::StringConstantsTraits<complementChar>::EmptyString();
 
/// An empty string of the strange character type.
inline constexpr StrangeString     EMPTY_STRANGE_STRING   = strings::StringConstantsTraits<strangeChar   >::EmptyString();
 
/// An empty string of the narrow character type.
inline constexpr NString           EMPTY_NSTRING          = strings::StringConstantsTraits<nchar         >::EmptyString();
 
/// An empty string of the wide character type.
inline constexpr WString           EMPTY_WSTRING          = strings::StringConstantsTraits<wchar         >::EmptyString();
 
/// An empty string of the complement character type.
inline constexpr XString           EMPTY_XSTRING          = strings::StringConstantsTraits<xchar         >::EmptyString();
 
// doxygen would consider the constructor call as a function call
#if DOXYGEN
/// A \e nulled string of the default character type.
inline constexpr  String           NULL_STRING;
 
/// A \e nulled string of the complement character type.
inline constexpr  ComplementString NULL_COMPLEMENT_STRING;
 
/// A \e nulled string of the strange character type.
inline constexpr  StrangeString    NULL_STRANGE_STRING;
 
/// A \e nulled string of the narrow character type.
inline constexpr NString           NULL_NSTRING;
 
/// A \e nulled string of the wide character type.
inline constexpr WString           NULL_WSTRING;
 
/// A \e nulled string of the complement character type.
inline constexpr XString           NULL_XSTRING;
#else
inline constexpr  String           NULL_STRING(nullptr);
inline constexpr  ComplementString NULL_COMPLEMENT_STRING(nullptr);
inline constexpr  StrangeString    NULL_STRANGE_STRING(nullptr);
inline constexpr NString           NULL_NSTRING(nullptr);
inline constexpr WString           NULL_WSTRING(nullptr);
inline constexpr XString           NULL_XSTRING(nullptr);
#endif
 
 
} // namespace [alib]