erfc(), erfcf(), erfcl()

Complementary error function

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():

Returns:

The value of the error function. For a correct value that would cause an underflow, these functions return 0.0 and a range error may occur.

If x is: These functions return:
NaN NaN
±0 +1
-Inf +2
+Inf +0

Errors:

FE_UNDERFLOW
The result underflows.

Classification:

ANSI, POSIX 1003.1

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