NAME¶

erf, erff, erfl, - error function

SYNOPSIS¶

#include <math.h>

double erf(double x);
float erff(float x);
long double erfl(long double x);

Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
erf(): erff(), erfl():

DESCRIPTION¶

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

erf(x) = 2/sqrt(pi)* integral from 0 to x of exp(-t*t) dt

RETURN VALUE¶

On success, these functions return the error function of x, a value in the range [-1, 1]. If x is a NaN, a NaN is returned. If x is +0 (-0), +0 (-0) is returned. If x is positive infinity (negative infinity), +1 (-1) is returned. If x is subnormal, a range error occurs, and the return value is 2*x/sqrt(pi).

ERRORS¶

See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur:

Range error: result underflow (x is subnormal)

An underflow floating-point exception (FE_UNDERFLOW) is raised.

These functions do not set errno.

ATTRIBUTES¶

Multithreading (see pthreads(7))¶

The erf(), erff(), and erfl() functions are thread-safe.

CONFORMING TO¶

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.

SEE ALSO¶

cerf(3), erfc(3), exp(3)

COLOPHON¶

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