Updated: April 19, 2023 |

*Complementary error function*

#include <math.h> double erfc ( doublex); float erfcf ( floatx); long double erfcl( long doublex);

`x`- The number for which you want to compute the complementary error function.

- 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 erfc(), erfcf(), and erfcl()
functions calculate the
complementary error function of `x`
(i.e., the result of the error function,
erf(),
subtracted from 1.0).
This is useful because the error function isn't very accurate
when `x` is large.

The erf() function computes:

This equality is true: erfc(-`x`) = 2 - erfc(`x`)

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

- Call
`feclearexcept(FE_ALL_EXCEPT)`before calling erfc(), erfcf(), or erfcl(). - On return, if
`fetestexcept(FE_ALL_EXCEPT)`is nonzero, then an error has occurred.

The value of the error function.

If x is: |
These functions return: | Errors: |
---|---|---|

±0.0 | 1.0 | — |

A value that would cause underflow | 0.0 | FE_UNDERFLOW |

-Inf | 2.0 | — |

Inf | 0.0 | — |

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 |