NAME

erf, erfc − error function and complementary error function

SYNOPSIS

#include <math.h>

double erf(double x);

double erfc(double x);

DESCRIPTION

erf() returns the error function of x, defined as:

{2 over sqrt pi} int from 0 to x e sup {- t sup 2} dt . 

erfc(), which returns 1.0 − erf(x) , is provided because of the extreme loss of relative accuracy if erf(x) is called for large x and the result subtracted from 1.0 (for example, for x = 5, twelve places are lost). 

erf() returns 1.0 when x is +INFINITY , or −1.0 when x is −INFINITY . 

erfc() returns 0.0 when x is +INFINITY , or 2.0 when x is −INFINITY . 

ERRORS

erf() and erfc() return NaN and set errno to EDOM when x is NaN. 

SEE ALSO

isinf(3M), isnan(3M), exp(3M). 

STANDARDS CONFORMANCE

erf() in libm.a: AES, SVID2, XPG2, XPG3
erf() in libM.a: AES, XPG3, XPG4

erfc() in libm.a: AES, SVID2, XPG2, XPG3
erfc() in libM.a: AES, XPG3, XPG4

Hewlett-Packard Company  —  HP-UX Release 9.10: April 1995