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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |VERSIONS |STANDARDS |HISTORY |SEE ALSO |COLOPHON | |
isgreater(3) Library Functions Manualisgreater(3)isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered - floating-point relational tests without exception for NaN
Math library (libm,-lm)
#include <math.h>int isgreater(x,y);int isgreaterequal(x,y);int isless(x,y);int islessequal(x,y);int islessgreater(x,y);int isunordered(x,y); Feature Test Macro Requirements for glibc (seefeature_test_macros(7)): All functions described here: _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
The normal relational operations (like<, "less than") fail if one of the operands is NaN. This will cause an exception. To avoid this, C99 defines the macros listed below. These macros are guaranteed to evaluate their arguments only once. The arguments must be of real floating-point type (note: do not pass integer values as arguments to these macros, since the arguments willnot be promoted to real-floating types).isgreater() determines(x) > (y) without an exception ifx ory is NaN.isgreaterequal() determines(x) >= (y) without an exception ifx ory is NaN.isless() determines(x) < (y) without an exception ifx ory is NaN.islessequal() determines(x) <= (y) without an exception ifx ory is NaN.islessgreater() determines(x) < (y) || (x) > (y) without an exception ifx ory is NaN. This macro is not equivalent tox != y because that expression is true ifx ory is NaN.isunordered() determines whether its arguments are unordered, that is, whether at least one of the arguments is a NaN.
The macros other thanisunordered() return the result of the relational comparison; these macros return 0 if either argument is a NaN.isunordered() returns 1 ifx ory is NaN and 0 otherwise.
No errors occur.
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────────┼───────────────┼─────────┤ │isgreater(),isgreaterequal(), │ Thread safety │ MT-Safe │ │isless(),islessequal(), │ │ │ │islessgreater(),isunordered() │ │ │ └──────────────────────────────────────┴───────────────┴─────────┘
Not all hardware supports these functions, and where hardware support isn't provided, they will be emulated by macros. This will result in a performance penalty. Don't use these functions if NaN is of no concern for you.
C11, POSIX.1-2008.
POSIX.1-2001, C99.
fpclassify(3),isnan(3)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17isgreater(3)Pages that refer to this page:fpclassify(3), math_error(7)
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