fdim(), fdimf(), fdiml()

Compute the positive difference between two floating-point numbers


#include <math.h>

double fdim( double x,
             double y );

float fdimf( float x,
             float y );

long double fdiml( long double x,
                   long double y );


x, y
The numbers that you want to compute the difference between.


The general-purpose math library.
(QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.


The fdim(), fdimf(), and fdiml() functions compute the positive difference between two floating-point numbers. If x is greater than y, then these function return x - y. If x is less than or equal to y, these functions return +0.

To check for error situations, use feclearexcept() and fetestexcept(). For example:


The positive difference.

If: These functions return: Errors:
x - y is positive and overflows Inf FE_OVERFLOW
The correct value would cause underflow The correct value, after rounding
x or y is NaN NaN

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.


C11, POSIX 1003.1

Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes