2004-11-03 13:51:07 +00:00
|
|
|
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
|
2007-06-20 22:33:04 +00:00
|
|
|
.TH "LDEXP" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
|
2004-11-03 13:51:07 +00:00
|
|
|
.\" ldexp
|
2007-09-20 06:03:25 +00:00
|
|
|
.SH PROLOG
|
|
|
|
This manual page is part of the POSIX Programmer's Manual.
|
|
|
|
The Linux implementation of this interface may differ (consult
|
|
|
|
the corresponding Linux manual page for details of Linux behavior),
|
|
|
|
or the interface may not be implemented on Linux.
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH NAME
|
|
|
|
ldexp, ldexpf, ldexpl \- load exponent of a floating-point number
|
|
|
|
.SH SYNOPSIS
|
|
|
|
.LP
|
|
|
|
\fB#include <math.h>
|
|
|
|
.br
|
|
|
|
.sp
|
|
|
|
double ldexp(double\fP \fIx\fP\fB, int\fP \fIexp\fP\fB);
|
|
|
|
.br
|
|
|
|
float ldexpf(float\fP \fIx\fP\fB, int\fP \fIexp\fP\fB);
|
|
|
|
.br
|
|
|
|
long double ldexpl(long double\fP \fIx\fP\fB, int\fP \fIexp\fP\fB);
|
|
|
|
.br
|
|
|
|
\fP
|
|
|
|
.SH DESCRIPTION
|
|
|
|
.LP
|
|
|
|
These functions shall compute the quantity \fIx\fP\ *\ 2**\fIexp\fP.
|
|
|
|
.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 \fIx\fP multiplied
|
|
|
|
by 2, raised to the power \fIexp\fP.
|
|
|
|
.LP
|
|
|
|
If these functions would cause overflow, a range error shall occur
|
|
|
|
and \fIldexp\fP(), \fIldexpf\fP(), and \fIldexpl\fP()
|
|
|
|
shall return \(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL (according
|
|
|
|
to the sign of \fIx\fP), respectively.
|
|
|
|
.LP
|
|
|
|
If the correct value would cause underflow, and is not representable,
|
|
|
|
a range error may occur, and \ either 0.0 (if
|
|
|
|
supported), or \ an implementation-defined value shall be
|
|
|
|
returned.
|
|
|
|
.LP
|
|
|
|
If
|
|
|
|
\fIx\fP is NaN, a NaN shall be returned.
|
|
|
|
.LP
|
|
|
|
If \fIx\fP is \(+-0 or \(+-Inf, \fIx\fP shall be returned.
|
|
|
|
.LP
|
|
|
|
If \fIexp\fP is 0, \fIx\fP shall be returned.
|
|
|
|
.LP
|
|
|
|
If the correct value would cause underflow, and is representable,
|
|
|
|
a range error may occur and the correct value shall be
|
|
|
|
returned.
|
|
|
|
.SH ERRORS
|
|
|
|
.LP
|
|
|
|
These functions shall fail if:
|
|
|
|
.TP 7
|
|
|
|
Range\ Error
|
|
|
|
The result overflows.
|
|
|
|
.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 overflow floating-point exception shall be
|
|
|
|
raised.
|
|
|
|
.sp
|
|
|
|
.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
|
|
|
|
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
|
2007-09-20 06:11:55 +00:00
|
|
|
\fIfeclearexcept\fP(), \fIfetestexcept\fP(), \fIfrexp\fP(), \fIisnan\fP()
|
2004-11-03 13:51:07 +00:00
|
|
|
, 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 .
|