fdim
Section: C Library Functions (3)
Updated: 2026-02-08
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NAME
fdim, fdimf, fdiml - positive difference
LIBRARY
Math library
(
libm,~
-lm)
SYNOPSIS
#include <math.h>
double fdim(double x, double y);
float fdimf(float x, float y);
long double fdiml(long double x, long double y);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
fdimf(),
fdiml():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
DESCRIPTION
These functions return the positive difference,
max(x-y,0),
between their arguments.
RETURN VALUE
On success, these functions return the positive difference.
If
x
or
y
is a NaN, a NaN is returned.
If the result overflows,
a range error occurs,
and the functions return
HUGE_VAL,
HUGE_VALF,
or
HUGE_VALL,
respectively.
ERRORS
See
math_error(7)
for information on how to determine whether an error has occurred
when calling these functions.
The following errors can occur:
- Range error: result overflow
-
errno
is set to
ERANGE.
An overflow floating-point exception
(FE_OVERFLOW)
is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
fdim(),
fdimf(),
fdiml()
| Thread safety | MT-Safe
|
STANDARDS
C11, POSIX.1-2008.
HISTORY
glibc 2.1.
C99, POSIX.1-2001.
BUGS
Before glibc 2.24
on certain architectures (e.g., x86, but not x86_64)
these functions did not set
errno.
SEE ALSO
fmax(3)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- STANDARDS
-
- HISTORY
-
- BUGS
-
- SEE ALSO
-
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