mirror of https://github.com/mkerrisk/man-pages
137 lines
3.5 KiB
Groff
137 lines
3.5 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
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.\" Modified 2002-07-27 by Walter Harms
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.\" (walter.harms@informatik.uni-oldenburg.de)
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.\"
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.TH FREXP 3 2008-10-29 "" "Linux Programmer's Manual"
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.SH NAME
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frexp, frexpf, frexpl \- convert floating-point number to fractional
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and integral components
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.sp
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.BI "double frexp(double " x ", int *" exp );
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.br
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.BI "float frexpf(float " x ", int *" exp );
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.br
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.BI "long double frexpl(long double " x ", int *" exp );
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.fi
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.sp
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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.BR frexpf (),
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.BR frexpl ():
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.RS 4
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE;
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.br
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or
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.I cc\ -std=c99
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.RE
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.ad
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.SH DESCRIPTION
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The
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.BR frexp ()
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function is used to split the number \fIx\fP into a
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normalized fraction and an exponent which is stored in \fIexp\fP.
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.SH "RETURN VALUE"
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The
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.BR frexp ()
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function returns the normalized fraction.
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If the argument \fIx\fP is not zero,
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the normalized fraction is \fIx\fP times a power of two,
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and its absolute value is always in the range 1/2 (inclusive) to
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1 (exclusive), that is, [0.5,1).
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If \fIx\fP is zero, then the normalized fraction is
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zero and zero is stored in \fIexp\fP.
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If
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.I x
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is a NaN,
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a NaN is returned, and the value of
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.I *exp
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is unspecified.
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If
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.I x
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is positive infinity (negative infinity),
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positive infinity (negative infinity) is returned, and the value of
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.I *exp
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is unspecified.
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.SH ERRORS
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No errors occur.
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.SH "CONFORMING TO"
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C99, POSIX.1-2001.
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The variant returning
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.I double
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also conforms to
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SVr4, 4.3BSD, C89.
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.SH EXAMPLE
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The program below produces results such as the following:
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.sp
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.nf
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.in +4n
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.RB "$" " ./a.out 2560"
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frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
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.RB "$" " ./a.out \-4"
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frexp(\-4, &e) = \-0.5: \-0.5 * 2^3 = -4
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.in
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.fi
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.SS Program source
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\&
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.nf
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#include <math.h>
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#include <float.h>
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#include <stdio.h>
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#include <stdlib.h>
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int
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main(int argc, char *argv[])
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{
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double x, r;
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int exp;
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x = strtod(argv[1], NULL);
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r = frexp(x, &exp);
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printf("frexp(%g, &e) = %g: %g * %d^%d = %g\\n",
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x, r, r, FLT_RADIX, exp, x);
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exit(EXIT_SUCCESS);
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} /* main */
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.fi
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.SH "SEE ALSO"
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.BR ldexp (3),
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.BR modf (3)
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