elvisoperator.cpp

// #################################################################################################
//  ALib C++ Library
//
//  Copyright 2013-2025 A-Worx GmbH, Germany
//  Published under 'Boost Software License' (a free software license, see LICENSE.txt)
// #################################################################################################
#include "alib_precompile.hpp"
#if !defined(ALIB_C20_MODULES) || ((ALIB_C20_MODULES != 0) && (ALIB_C20_MODULES != 1))
#   error "Symbol ALIB_C20_MODULES has to be given to the compiler as either 0 or 1"
#endif
#if ALIB_C20_MODULES
    module;
#endif
// ======================================   Global Fragment   ======================================
#include "alib/expressions/expressions.prepro.hpp"
 
// ===========================================   Module   ==========================================
#if ALIB_C20_MODULES
    module ALib.Expressions.Impl;
    import   ALib.Characters.Functions;
    import   ALib.Strings;
#else
#   include "ALib.Characters.Functions.H"
#   include "ALib.Strings.H"
#   include "ALib.Expressions.Impl.H"
#endif
// ======================================   Implementation   =======================================
//! @cond NO_DOX
namespace alib {  namespace expressions { namespace plugins {
 
ElvisOperator::ElvisOperator( Compiler& compiler )
: CompilerPlugin("ALib Elvis", compiler, CompilePriorities::ElvisOperator )
{}
 
namespace {
 
Box elvis( Scope&, ArgIterator  arg, ArgIterator )
{
    return (*arg).Call<FIsTrue>() ? *arg : *(arg + 1);
}
 
} // anonymous namespace
 
bool ElvisOperator::TryCompilation( CIBinaryOp&   ciBinaryOp    )
{
    Box& lhs= * ciBinaryOp.ArgsBegin;
    Box& rhs= *(ciBinaryOp.ArgsBegin + 1);
 
    // not Elvis operator  A_CHAR("A ?: B") ?
    if( ciBinaryOp.Operator != A_CHAR("?:") || !lhs.IsSameType(rhs) )
        return false;
 
    ALIB_DBG( ciBinaryOp.DbgCallbackName = "elvis";      )
 
    // constant A?
    if( ciBinaryOp.LhsIsConst )
    {
        if( lhs.Call<FIsTrue>() )
            ciBinaryOp.TypeOrValue= lhs;
        else
        {
            // constant B?
            if( ciBinaryOp.RhsIsConst )
                ciBinaryOp.TypeOrValue= rhs;
            else
                ciBinaryOp.NonConstArgIsResult= true;
        }
        return true;
    }
 
    // non constant A
    ciBinaryOp.Callback   = elvis;
    ciBinaryOp.TypeOrValue= rhs;
 
    return true;
}
 
}}} // namespace [alib::expressions::detail]
//! @endcond