erf(3) — Linux manual page

erf(3)                  Library Functions Manual                  erf(3)

NAME

       erf, erff, erfl - error function

LIBRARY

       Math library (libm, -lm)

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_SOURCE

       erff(), erfl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

       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, 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

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ erf(), erff(), erfl()               │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       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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Linux man-pages 6.9.1          2024-05-02                         erf(3)

Pages that refer to this page: erfc(3)

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