c99 [ flag... ] file... –lm [ library... ] #include <math.h> double fdim(double x, double y);
float fdimf(float x, float y);
long double fdiml(long double x, long double y);
These functions determine the positive difference between their arguments. If x is greater than y, x−y is returned. If x is less than or equal to y, +0 is returned.
Upon successful completion, these functions return the positive difference value.
If x−y is positive and overflows, a range error occurs and fdim(), fdimf(), and fdiml() returns the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If x or y is NaN, a NaN is returned.
These functions will fail if:
The result overflows.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception will be raised.
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.
See attributes(5) for descriptions of the following attributes: