man3/modf.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" References consulted:
   6 .\"     Linux libc source code
   7 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
   8 .\"     386BSD man pages
   9 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  10 .\" Modified 2002-07-27 by Walter Harms
  11 .\"     (walter.harms@informatik.uni-oldenburg.de)
  12 .\"
  13 .TH MODF 3 2021-03-22 "Linux man-pages (unreleased)"
  14 .SH NAME
  15 modf, modff, modfl \- extract signed integral and fractional values from
  16 floating-point number
  17 .SH LIBRARY
  18 Math library
  19 .RI ( libm ", " \-lm )
  20 .SH SYNOPSIS
  21 .nf
  22 .B #include <math.h>
  23 .PP
  24 .BI "double modf(double " x ", double *" iptr );
  25 .BI "float modff(float " x ", float *" iptr );
  26 .BI "long double modfl(long double " x ", long double *" iptr );
  27 .fi
  28 .PP
  29 .RS -4
  30 Feature Test Macro Requirements for glibc (see
  31 .BR feature_test_macros (7)):
  32 .RE
  33 .PP
  34 .BR modff (),
  35 .BR modfl ():
  36 .nf
  37     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  38         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  39         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  40 .fi
  41 .SH DESCRIPTION
  42 These functions break the argument
  43 .I x
  44 into an integral
  45 part and a fractional part, each of which has the same sign as
  46 .IR x .
  47 The integral part is stored in the location pointed to by
  48 .IR iptr .
  49 .SH RETURN VALUE
  50 These functions return the fractional part of
  51 .IR x .
  52 .PP
  53 If
  54 .I x
  55 is a NaN, a NaN is returned, and
  56 .I *iptr
  57 is set to a NaN.
  58 .PP
  59 If
  60 .I x
  61 is positive infinity (negative infinity), +0 (\-0) is returned, and
  62 .I *iptr
  63 is set to positive infinity (negative infinity).
  64 .SH ERRORS
  65 No errors occur.
  66 .SH ATTRIBUTES
  67 For an explanation of the terms used in this section, see
  68 .BR attributes (7).
  69 .ad l
  70 .nh
  71 .TS
  72 allbox;
  73 lbx lb lb
  74 l l l.
  75 Interface       Attribute       Value
  76 T{
  77 .BR modf (),
  78 .BR modff (),
  79 .BR modfl ()
  80 T}      Thread safety   MT-Safe
  81 .TE
  82 .hy
  83 .ad
  84 .sp 1
  85 .SH STANDARDS
  86 C99, POSIX.1-2001, POSIX.1-2008.
  87 .PP
  88 The variant returning
  89 .I double
  90 also conforms to
  91 SVr4, 4.3BSD, C89.
  92 .SH SEE ALSO
  93 .BR frexp (3),
  94 .BR ldexp (3)