erf - Online Linux Manual PageSection : 3
Updated : 2023-02-05
Source : Linux man-pages 6.03

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NAMEerf, erff, erfl − error function

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LIBRARYMath library (libm, −lm)

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SYNOPSIS#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)): erf(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEerff(), erfl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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DESCRIPTIONThese functions return the error function of x, defined as erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(−t*t) dt

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RETURN VALUEOn success, these functions return the value of 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).

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ERRORSSee 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.

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ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7). InterfaceAttributeValue erf(), erff(), erfl() Thread safetyMT-Safe

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STANDARDSC99, POSIX.1-2001, POSIX.1-2008. The variant returning double also conforms to SVr4, 4.3BSD.

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SEE ALSOcerf(3), erfc(3), exp(3) 0

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