erfc(), erfcf(), erfcl()

Synopsis:

#include <math.h>

double erfc ( double x );

float erfcf ( float x );

long double erfcl( long double x );

Arguments:

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

Library:

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.

Description:

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.

Returns:

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.

Classification:

C11, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	Yes
Signal handler	Yes
Thread	Yes