1ERF(P)                     POSIX Programmer's Manual                    ERF(P)
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NAME

6       erf, erff, erfl - error functions
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SYNOPSIS

9       #include <math.h>
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11       double erf(double x);
12       float erff(float x);
13       long double erfl(long double x);
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DESCRIPTION

17       These  functions  shall compute the error function of their argument x,
18       defined as:
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20       An application wishing to check for error situations should  set  errno
21       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
22       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
23       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
24       occurred.
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RETURN VALUE

27       Upon successful completion, these functions shall return the  value  of
28       the error function.
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30       If x is NaN, a NaN shall be returned.
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32       If x is ±0, ±0 shall be returned.
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34       If x is ±Inf, ±1 shall be returned.
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36       If  x is subnormal, a range error may occur, and 2 * x/ sqrt(pi) should
37       be returned.
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ERRORS

40       These functions may fail if:
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42       Range Error
43              The result underflows.
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45       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
46       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
47       (math_errhandling & MATH_ERREXCEPT) is  non-zero,  then  the  underflow
48       floating-point exception shall be raised.
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51       The following sections are informative.
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EXAMPLES

54       None.
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APPLICATION USAGE

57       Underflow occurs when |x| < DBL_MIN * ( sqrt(pi)/2).
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59       On   error,   the   expressions  (math_errhandling  &  MATH_ERRNO)  and
60       (math_errhandling & MATH_ERREXCEPT) are independent of each other,  but
61       at least one of them must be non-zero.
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RATIONALE

64       None.
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FUTURE DIRECTIONS

67       None.
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SEE ALSO

70       erfc()  , feclearexcept() , fetestexcept() , isnan() , the Base Defini‐
71       tions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of  Error
72       Conditions for Mathematical Functions, <math.h>
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75       Portions  of  this text are reprinted and reproduced in electronic form
76       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
77       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
78       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
79       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
80       event of any discrepancy between this version and the original IEEE and
81       The  Open Group Standard, the original IEEE and The Open Group Standard
82       is the referee document. The original Standard can be  obtained  online
83       at http://www.opengroup.org/unix/online.html .
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87IEEE/The Open Group                  2003                               ERF(P)
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