Trigraphs are more problematic to the unaware user than digraphs. This is because they are replaced within string literals and comments. Here are some examples… Example A: std::string example = “What??!??!”; std::cout << example << std::endl; What|| will be printed to the console. This is because of the trigraph ??! being translated to |. Example … Read more
I don’t know for sure, but you’re most likely to find digraphs and trigraphs being used in IBM mainframe environments. The EBCDIC character set doesn’t include some characters that are required for C. The other justification for digraphs and trigraphs, 7-bit ASCII-ish character sets that replace some punctuation characters with accented letters, is probably less … Read more
From the first ISO C++ standard C++98, this is described in 2.5/ Alternative tokens [lex.digraph]: Alternative token representations are provided for some operators and punctuators. In all respects of the language, each alternative token behaves the same, respectively, as its primary token, except for its spelling. The set of alternative tokens is defined in Table … Read more
Digraphs were created for programmers that didn’t have a keyboard which supported the ISO 646 character set. http://en.wikipedia.org/wiki/C_trigraph
The line: while( a[ 0xFULL?’\0′:-1:>>>=a<:!!0X.1P1 ] ) contains the digraphs :> and <:, which translate to ] and [ respectively, so it’s equivalent to: while( a[ 0xFULL?’\0′:-1 ] >>= a[ !!0X.1P1 ] ) The literal 0xFULL is the same as 0xF (which is hex for 15); the ULL just specifies that it’s an unsigned long … Read more
The program uses digraphs to represent the following: [] {}; This is a lambda expression that does nothing. The corresponding symbols have these equivalents: <: = [ %> = } Though they are generally unneeded today, digraphs are useful for when your keyboard lacks certain keys necessary to use C++’s basic source character set, namely … Read more