fdim(), fdimf(), fdiml()
QNX SDP8.0C Library ReferenceAPIDeveloper
Compute the positive difference between two floating-point numbers
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 );
Arguments:
- x, y
- The numbers that you want to compute the difference between.
Library:
- libm
- The general-purpose math library.
- libm-sve
- 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:
- If you want only selected processes to run with the SVE version, you can include both libraries in your OS image and use the -l m or -l m-sve option to qcc to link explicitly against the appropriate one.
- If you want all processes to use the SVE version, include libm-sve.so in your OS image and set up a symbolic link from libm.so to libm-sve.so. Use the -l m option to qcc to link against the library.
Note:
Compile your program with the -fno-builtin option to prevent the compiler from using a
built-in version of the function.
Description:
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:
- Call
feclearexcept(FE_ALL_EXCEPT)before calling fdim(), fdimf(), or fdiml(). - On return, if
fetestexcept(FE_ALL_EXCEPT)is nonzero, then an error has occurred.
Returns:
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.
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
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