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erf - Man Page

error function


Math library (libm, -lm)


#include <math.h>

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

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

erff(), erfl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


These functions return 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 value of the error function of x, a value in the range [-1,Ā 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).


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.


For an explanation of the terms used in this section, see attributes(7).

erf(), erff(), erfl()Thread safetyMT-Safe


C11, POSIX.1-2008.


C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD.

See Also

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

Referenced By

cerf(3), cerfcx(3), cerfi(3), erfc(3), unu-1op(1).

The man pages erff(3) and erfl(3) are aliases of erf(3).

2024-05-02 Linux man-pages 6.9.1