NAME

erf, erfc − error function and complementary error function

SYNOPSIS

#include <math.h>

double erf (x)
double x;

double erfc (x)
double x;

DESCRIPTION

Erf returns the error function of x, defined as {2 over down 50 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). 

DEPENDENCIES

Series 800 (/lib/libm.a and ANSI C /lib/libM.a)
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

Series 800 (/lib/libm.a and ANSI C /lib/libM.a)
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: SVID2, XPG2, XPG3

erfc: SVID2, XPG2, XPG3

Hewlett-Packard Company  —  HP-UX Release 7.0: Sept 1989