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man:erff

ERF(3) Linux Programmer's Manual ERF(3)

NAME

`     erf, erff, erfl, - error function`

SYNOPSIS

`     #include <math.h>`
```     double erf(double x);
float erff(float x);
long double erfl(long double x);```
`     Link with -lm.`
` 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 versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
erff(), erfl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 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 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).```
```     allbox; lbw21 lb lb l l l.  Interface Attribute Value T{ erf(), erff(),
erfl() T}   Thread safety  MT-Safe```

CONFORMING TO

`     C99, POSIX.1-2001, POSIX.1-2008.`
`     The variant returning double also conforms to SVr4, 4.3BSD.`

SEE ALSO

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

COLOPHON

```     This  page  is  part of release 4.16 of the Linux man-pages project.  A
description of the project, information about reporting bugs,  and  the
latest     version     of     this    page,    can    be    found    at
https://www.kernel.org/doc/man-pages/.```

GNU 2017-09-15 ERF(3)

/data/webs/external/dokuwiki/data/pages/man/erff.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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