erf(3) - f39

1erf(3)                     Library Functions Manual                     erf(3)
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NAME

6       erf, erff, erfl - error function
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LIBRARY

9       Math library (libm, -lm)
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SYNOPSIS

12       #include <math.h>
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14       double erf(double x);
15       float erff(float x);
16       long double erfl(long double x);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       erf():
21           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
22               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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25       erff(), erfl():
26           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
27               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
28               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

31       These functions return the error function of x, defined as
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33           erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(-t*t) dt
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RETURN VALUE

36       On  success,  these functions return the value of the error function of
37       x, a value in the range [-1, 1].
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39       If x is a NaN, a NaN is returned.
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41       If x is +0 (-0), +0 (-0) is returned.
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43       If x is positive infinity (negative infinity), +1 (-1) is returned.
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45       If x is subnormal, a range  error  occurs,  and  the  return  value  is
46       2*x/sqrt(pi).
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ERRORS

49       See  math_error(7) for information on how to determine whether an error
50       has occurred when calling these functions.
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52       The following errors can occur:
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54       Range error: result underflow (x is subnormal)
55              An underflow floating-point exception (FE_UNDERFLOW) is raised.
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57       These functions do not set errno.
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ATTRIBUTES

60       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
61       tributes(7).
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63       ┌────────────────────────────────────────────┬───────────────┬─────────┐
64       │Interface                                   │ Attribute     │ Value   │
65       ├────────────────────────────────────────────┼───────────────┼─────────┤
66       │erf(), erff(), erfl()                       │ Thread safety │ MT-Safe │
67       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

70       C11, POSIX.1-2008.
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HISTORY

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