Updated: April 19, 2023 |

*Compute the positive difference between two floating-point numbers*

#include <math.h> double fdim( doublex, doubley); float fdimf( floatx, floaty); long double fdiml( long doublex, long doubley);

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

- libm
- The general-purpose math library.
- libm-sve
- (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:

- 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.

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.

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.

Safety: | |
---|---|

Cancellation point | No |

Interrupt handler | Yes |

Signal handler | Yes |

Thread | Yes |