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'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" 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 modf 3 2023-03-30 "Linux man-pages 6.04"
.SH NAME
modf, modff, modfl \- extract signed integral and fractional values from
floating-point number
.SH LIBRARY
Math library
.RI ( libm ", " \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.PP
.BI "double modf(double " x ", double *" iptr );
.BI "float modff(float " x ", float *" iptr );
.BI "long double modfl(long double " x ", long double *" iptr );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR modff (),
.BR modfl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions break the argument
.I x
into an integral
part and a fractional part, each of which has the same sign as
.IR x .
The integral part is stored in the location pointed to by
.IR iptr .
.SH RETURN VALUE
These functions return the fractional part of
.IR x .
.PP
If
.I x
is a NaN, a NaN is returned, and
.I *iptr
is set to a NaN.
.PP
If
.I x
is positive infinity (negative infinity), +0 (\-0) is returned, and
.I *iptr
is set to positive infinity (negative infinity).
.SH ERRORS
No errors occur.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.BR modf (),
.BR modff (),
.BR modfl ()
T} Thread safety MT-Safe
.TE
.hy
.ad
.sp 1
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.PP
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH SEE ALSO
.BR frexp (3),
.BR ldexp (3)
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