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

Use the -l m option to qcc to link against this library.

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:

ANSI, POSIX 1003.1

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