FDIM(3) Linux Programmer's Manual FDIM(3)

fdim, fdimf, fdiml - positive difference

#include <math.h>
double fdim(double x, double y);
float fdimf(float x, float y);
long double fdiml(long double x, long double y);
Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
fdimf(), fdiml():

These functions return the positive difference, max( x-y,0), between their arguments.

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.

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
An overflow floating-point exception (FE_OVERFLOW) is raised.
These functions do not set errno.

These functions first appeared in glibc in version 2.1.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
fdim (), fdimf (), fdiml () Thread safety MT-Safe

C99, POSIX.1-2001, POSIX.1-2008.