man3/frexp.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  28 .\" Modified 2002-07-27 by Walter Harms
  29 .\"     (walter.harms@informatik.uni-oldenburg.de)
  30 .\"
  31 .TH FREXP 3 2002-07-27 "" "Linux Programmer's Manual"
  32 .SH NAME
  33 frexp, frexpf, frexpl \- convert floating-point number to fractional
  34 and integral components
  35 .SH SYNOPSIS
  36 .nf
  37 .B #include <math.h>
  38 .sp
  39 .BI "double frexp(double " x ", int *" exp );
  40 .br
  41 .BI "float frexpf(float " x ", int *" exp );
  42 .br
  43 .BI "long double frexpl(long double " x ", int *" exp );
  44 .fi
  45 .sp
  46 Link with \-lm.
  47 .SH DESCRIPTION
  48 The \fBfrexp()\fP function is used to split the number \fIx\fP into a
  49 normalized fraction and an exponent which is stored in \fIexp\fP.
  50 .SH "RETURN VALUE"
  51 The \fBfrexp()\fP function returns the normalized fraction.  If the
  52 argument \fIx\fP is not zero, the normalized fraction is \fIx\fP
  53 times a power of two, and is always in the range 1/2 (inclusive) to
  54 1 (exclusive).  If \fIx\fP is zero, then the normalized fraction is
  55 zero and zero is stored in \fIexp\fP.
  56 .SH "CONFORMING TO"
  57 SVID 3, POSIX, BSD 4.3, ISO 9899.
  58 The float and the long double variants are C99 requirements.
  59 .SH EXAMPLE
  60 .nf
  61 #include <stdio.h>
  62 #include <math.h>
  63 #include <float.h>
  64 int main () {
  65         double d = 2560;
  66         int e;
  67         double f = frexp(d, &e);
  68         printf("frexp(%g, &e) = %g: %g * %d^%d = %g\en",
  69                d, f, f, FLT_RADIX, e, d);
  70         return 0;
  71 }
  72 .fi
  73 .sp
  74 This program prints
  75 .sp
  76 .in +5
  77 frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
  78 .in
  79 .SH "SEE ALSO"
  80 .BR ldexp (3),
  81 .BR modf (3)