NAME
erf, erff, erfl, - error function SYNOPSIS
#include
double erf(double x); float erff(float x); long double erfl(long double x); Link with -lm. Feature Test Macro Requirements for glibc (see featuretestmacros(7)): erf(): BSDSOURCE || SVIDSOURCE || XOPENSOURCE || ISOC99SOURCE || POSIXCSOURCE >= 200112L;
or cc -std=c99 erff(), erfl(): BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 || ISOC99SOURCE || POSIXCSOURCE >= 200112L;
or cc -std=c99 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 matherror(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 (FEUNDERFLOW) is raised. These functions do not set errno. ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├──────────────────────┼───────────────┼─────────┤
│erf(), erff(), erfl() │ Thread safety │ MT-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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GNU 2010-09-20 ERF(3)