mirror of https://github.com/mkerrisk/man-pages
92 lines
2.7 KiB
Plaintext
92 lines
2.7 KiB
Plaintext
|
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
|
||
|
.TH "ERF" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
|
||
|
.\" erf
|
||
|
.SH NAME
|
||
|
erf, erff, erfl \- error functions
|
||
|
.SH SYNOPSIS
|
||
|
.LP
|
||
|
\fB#include <math.h>
|
||
|
.br
|
||
|
.sp
|
||
|
double erf(double\fP \fIx\fP\fB);
|
||
|
.br
|
||
|
float erff(float\fP \fIx\fP\fB);
|
||
|
.br
|
||
|
long double erfl(long double\fP \fIx\fP\fB);
|
||
|
.br
|
||
|
\fP
|
||
|
.SH DESCRIPTION
|
||
|
.LP
|
||
|
These functions shall compute the error function of their argument
|
||
|
\fIx\fP, defined as:
|
||
|
.LP
|
||
|
An application wishing to check for error situations should set \fIerrno\fP
|
||
|
to zero and call
|
||
|
\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
|
||
|
On return, if \fIerrno\fP is non-zero or
|
||
|
\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
|
||
|
is non-zero, an error has occurred.
|
||
|
.SH RETURN VALUE
|
||
|
.LP
|
||
|
Upon successful completion, these functions shall return the value
|
||
|
of the error function.
|
||
|
.LP
|
||
|
If
|
||
|
\fIx\fP is NaN, a NaN shall be returned.
|
||
|
.LP
|
||
|
If \fIx\fP is \(+-0, \(+-0 shall be returned.
|
||
|
.LP
|
||
|
If \fIx\fP is \(+-Inf, \(+-1 shall be returned.
|
||
|
.LP
|
||
|
If \fIx\fP is subnormal, a range error may occur, and 2 * \fIx\fP/
|
||
|
\fIsqrt\fP(pi) should
|
||
|
be returned.
|
||
|
.SH ERRORS
|
||
|
.LP
|
||
|
These functions may fail if:
|
||
|
.TP 7
|
||
|
Range\ Error
|
||
|
The result underflows.
|
||
|
.LP
|
||
|
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
|
||
|
then \fIerrno\fP shall be set to [ERANGE]. If the
|
||
|
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
|
||
|
then the underflow floating-point exception shall be
|
||
|
raised.
|
||
|
.sp
|
||
|
.LP
|
||
|
\fIThe following sections are informative.\fP
|
||
|
.SH EXAMPLES
|
||
|
.LP
|
||
|
None.
|
||
|
.SH APPLICATION USAGE
|
||
|
.LP
|
||
|
Underflow occurs when |\fIx\fP| < DBL_MIN * ( \fIsqrt\fP(pi)/2).
|
||
|
.LP
|
||
|
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling
|
||
|
& MATH_ERREXCEPT) are independent of
|
||
|
each other, but at least one of them must be non-zero.
|
||
|
.SH RATIONALE
|
||
|
.LP
|
||
|
None.
|
||
|
.SH FUTURE DIRECTIONS
|
||
|
.LP
|
||
|
None.
|
||
|
.SH SEE ALSO
|
||
|
.LP
|
||
|
\fIerfc\fP() , \fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIisnan\fP()
|
||
|
, the Base Definitions volume of
|
||
|
IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions
|
||
|
for
|
||
|
Mathematical Functions, \fI<math.h>\fP
|
||
|
.SH COPYRIGHT
|
||
|
Portions of this text are reprinted and reproduced in electronic form
|
||
|
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
|
||
|
-- Portable Operating System Interface (POSIX), The Open Group Base
|
||
|
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
|
||
|
Electrical and Electronics Engineers, Inc and The Open Group. In the
|
||
|
event of any discrepancy between this version and the original IEEE and
|
||
|
The Open Group Standard, the original IEEE and The Open Group Standard
|
||
|
is the referee document. The original Standard can be obtained online at
|
||
|
http://www.opengroup.org/unix/online.html .
|