erf(3) - Linux manual page (original) (raw)

erf(3) Library Functions Manual erf(3)

NAME top

   erf, erff, erfl - error function

LIBRARY top

   Math library (_libm_, _-lm_)

SYNOPSIS top

   **#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 top

   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 top

   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 top

   See [math_error(7)](../man7/math%5Ferror.7.html) 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](../man3/errno.3.html)_.

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **erf**(), **erff**(), **erfl**()                │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   C11, POSIX.1-2008.

HISTORY top

   C99, POSIX.1-2001.

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

SEE ALSO top

   **cerf**(3), [erfc(3)](../man3/erfc.3.html), [exp(3)](../man3/exp.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 erf(3)

Pages that refer to this page:erfc(3)