modf(3) — Linux manual pages

Linux manual pages	Section 3: Subroutines

Name

modf, modff, modfl — extract signed integral and fractional values from floating-point number

Synopsis

#include <math.h>

`double modf(`	double `x`,
	double *`iptr)`;

`float modff(`	float `x`,
	float *`iptr)`;

`long double modfl(`	long double `x`,
	long double *`iptr)`;

Note

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
`modf`(), `modfl`():
`_BSD_SOURCE` \|\| `_SVID_SOURCE` \|\| `_XOPEN_SOURCE` >= 600 \|\| `_ISOC99_SOURCE` \|\| `_POSIX_C_SOURCE` >= 200112L;
or cc `-std=c99`

	Note
	Link with `−lm`.

DESCRIPTION

The modf() function breaks the argument x into an integral part and a fractional part, each of which has the same sign as x. The integral part is stored in the location pointed to by iptr.

RETURN VALUE

The modf() function returns the fractional part of x.

If x is a NaN, a NaN is returned, and *iptr is set to a NaN.

If x is positive infinity (negative infinity), +0 (−0) is returned, and *iptr is set to positive infinity (negative infinity).

ERRORS

No errors occur.

ATTRIBUTES

Multithreading (see pthreads(7))

The modf(), modff(), and modfl() functions are thread-safe.

CONFORMING TO

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.

COLOPHON

This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.

  Copyright 1993 David Metcalfe (davidprism.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 (faithcs.unc.edu)
Modified 2002-07-27 by Walter Harms
(walter.harmsinformatik.uni-oldenburg.de)