Alternative operator representations
C++ (and C) source code may be written in any non-ASCII 7-bit character set that includes the ISO 646/ECMA-6 invariant character set. However, several C++ operators and punctuators require characters that are outside of the ISO 646 codeset: {, }, [, ], #, \, ^, |, ^. To be able to use character encodings where some or all of these symbols do not exist, C++ defines two kinds of alternatives: additional keywords that correspond to the operators that use these characters and special combinations of two or three ISO 646 compatible characters that are interpreted as if they were a single non-ISO 646 character.
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[edit] Alternative keywords
There are alternative spellings for several operators defined as keywords in the C++ standard.
| Primary | Alternative |
|---|---|
| && | and |
| &= | and_eq |
| & | bitand |
| | | bitor |
| ~ | compl |
| ! | not |
| != | not_eq |
| || | or |
| |= | or_eq |
| ^ | xor |
| ^= | xor_eq |
[edit] Compatibility with C
The same words are defined in the C programming language in the include file <iso646.h> as macros. Because in C++ these are language keywords, the C++ version of <iso646.h>, as well as <ciso646>, does not define anything.
[edit] Digraphs and trigraphs
The following combinations of two and three characters (digraphs and trigraphs) are valid substitutions for their respective primary characters:
| Primary | Digraph | Trigraph |
|---|---|---|
| { | <% | ??< |
| } | %> | ??> |
| [ | <: | ??( |
| ] | :> | ??) |
| # | %: | ??= |
| \ | ??/ | |
| ^ | ??' | |
| | | ??! | |
| ~ | ??- |
[edit] Keywords
and, and_eq, bitand, bitor, compl, not, not_eq, or, or_eq, xor, xor_eq
[edit] Example
The following example demonstrates the use of several alternative keywords:
%:include <iostream> int main(int argc, char *argv<::>) <% if (argc > 1 and argv<:1:> not_eq '\0') <% std::cout << "Hello " << argv<:1:> << '\n'; %> %>