C alternative tokens
| C standard library |
|---|
| General topics |
| Miscellaneous headers |
C alternative tokens refer to a set of alternative spellings of common operators in the C programming language. They are implemented as a group of macro constants in the C standard library in the iso646.h header. The tokens were added to the standard in a 1995 amendment to the C90 standard.
The alternative tokens allow programmers to use C language bitwise and logical operators which could otherwise be hard to type on some international and non-QWERTY keyboards. The name of the header file they are implemented in refers to the ISO/IEC 646 standard, a 7-bit character set with a number of regional variations, some of which have accented characters in place of the punctuation marks used by C operators.
The macros
The iso646.h header defines the following 11 macros as stated below:
| Macro | Defined as |
|---|---|
and |
&& |
and_eq |
&= |
bitand |
& |
bitor |
| |
compl |
~ |
not |
! |
not_eq |
!= |
or |
|| |
or_eq |
|= |
xor |
^ |
xor_eq |
^= |
C++
The above-mentioned identifiers are operator keywords in the ISO C++ programming language and do not require the inclusion of a header file.[2] For consistency, the C++98 standard provides the header <ciso646>. However the latter file has no effect, being empty.[3] Notwithstanding some compilers, such as Microsoft Visual C++, do require the header to be included in order to use these identifiers.
See also
References
- ^ "Rationale for International Standard - Programming Languages - C" (PDF). 5.10. April 2003. Archived (PDF) from the original on 2016-06-06. Retrieved 2010-10-17.
- ^ Stroustrup, Bjarne (1994-03-29). Design and Evolution of C++ (1st ed.). Addison-Wesley Publishing Company. ISBN 0-201-54330-3.
- ^ Lischner, Ray (2003). C++ in a Nutshell. O'Reilly Media. p. 212. ISBN 0-596-00298-X.
External links
- : alternative spellings – Base Definitions Reference, The Single UNIX® Specification, Issue 7 from The Open Group
