Alternative operator representations
C++ (and C) source code may be written in any non-ASCII 7-bit character set that includes the ISO 646:1983 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 (such as the German DIN 66003), 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.
| Contents | 
[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 | 
|---|---|---|
| { | <% | ??< | 
| } | %> | ??> | 
| [ | <: | ??( | 
| ] | :> | ??) | 
| # | %: | ??= | 
| \ | ??/ | |
| ^ | ??' | |
| | | ??! | |
| ~ | ??- | 
Note that trigraphs (but not digraphs) are parsed before comments and string literals are recognized, so a comment such as // Will the next line be executed?????/ will effectively comment out the following line, and the string literal such as "Enter date ??/??/??" is parsed as "Enter date \\??".
| When the parser meets the charater sequence <:: and the subsequent character is neither : nor >, the < is treated as a preprocessor token by itself and not as the first character of the alternative token <:. Thus std::vector<::std::string> won't be wrongly treated as std::vector[:std::string>. | (since C++11) | 
[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.
 
[edit] See also
| C documentation for Alternative operator representations | 


