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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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isgreater(3) Library Functions Manual isgreater(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 (see
feature_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 will not be promoted to real-floating types).
isgreater()
determines (x) > (y) without an exception if x or y is NaN.
isgreaterequal()
determines (x) >= (y) without an exception if x or y is
NaN.
isless()
determines (x) < (y) without an exception if x or y is NaN.
islessequal()
determines (x) <= (y) without an exception if x or y is
NaN.
islessgreater()
determines (x) < (y) || (x) > (y) without an exception if x
or y is NaN. This macro is not equivalent to x != y
because that expression is true if x or y is NaN.
isunordered()
determines whether its arguments are unordered, that is,
whether at least one of the arguments is a NaN.
The macros other than isunordered() return the result of the
relational comparison; these macros return 0 if either argument is
a NaN.
isunordered() returns 1 if x or y is NaN and 0 otherwise.
No errors occur.
For an explanation of the terms used in this section, see
attributes(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 the man-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
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⟨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-
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part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 isgreater(3)
Pages that refer to this page: fpclassify(3), math_error(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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