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erfc(), erfcf()

Complementary error function

Synopsis:

#include <math.h>

double erfc ( double x );

float erfcf ( float 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() and erfcf() 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)

Returns:

The value of the error function, or NAN if x is NAN.

If an error occurs, these functions return 0, but this is also a valid mathematical result. If you want to check for errors, set errno to 0, call the function, and then check errno again. These functions don't change errno if no errors occurred.

Classification:

ANSI, POSIX 1003.1

See also:

erf()