isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered -
floating-point relational tests without exception for NaN
#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);
Link with
-lm.
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 (), isless (), islessequal (),
islessgreater (), isunordered () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008, C99.
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.
fpclassify(3),
isnan(3)