elvisoperator.cpp

//! @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