ISGREATER(3) Linux Programmer's Manual ISGREATER(3)
isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered - floating-
point relational tests without exception for NaN
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: _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99
The normal relation operations (like <, "less than") will fail if one of the operands is
NaN. This will cause an exception. To avoid this, C99 defines these macros. The macros
are guaranteed to evaluate their operands only once. The operands can be of any real
determines (x) > (y) without an exception if x or y is NaN.
determines (x) >= (y) without an exception if x or y is NaN.
determines (x) < (y) without an exception if x or y is NaN.
determines (x) <= (y) without an exception if x or y is NaN.
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.
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.
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.
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