Minor wording changes.

[thirdparty/man-pages.git] / man3 / frexp.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.TH FREXP 3 2002-07-27 "" "Linux Programmer's Manual"
.SH NAME
frexp, frexpf, frexpl \- convert floating-point number to fractional
and integral components
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double frexp(double " x ", int *" exp );
.br
.BI "float frexpf(float " x ", int *" exp );
.br
.BI "long double frexpl(long double " x ", int *" exp );
.fi
.sp
Link with \fI\-lm\fP.
.SH DESCRIPTION
The
.BR frexp ()
function is used to split the number \fIx\fP into a
normalized fraction and an exponent which is stored in \fIexp\fP.
.SH "RETURN VALUE"
The
.BR frexp ()
function returns the normalized fraction.
If the argument \fIx\fP is not zero,
the normalized fraction is \fIx\fP times a power of two,
and its absolute value is always in the range 1/2 (inclusive) to
1 (exclusive).
If \fIx\fP is zero, then the normalized fraction is
zero and zero is stored in \fIexp\fP.
.SH "CONFORMING TO"
SVr4, 4.3BSD, C89, C99.
The
.I float
and
.I "long double"
variants are C99 requirements.
.SH EXAMPLE
.nf
#include <math.h>
#include <float.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
    double x, r;
    int exp;

    x = strtod(argv[1], NULL);
    r = frexp(x, &exp);

    printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n",
           x, r, r, FLT_RADIX, exp, x);
    exit(EXIT_SUCCESS);
} /* main */
.fi
.sp
This program produces results such as the following:
.sp
.nf
.in +4n
$ ./a.out 2560
frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
$ ./a.out \-4
frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = -4
.in
.fi
.SH "SEE ALSO"
.BR ldexp (3),
.BR modf (3)