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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 2023-10-31 "Linux man-pages 6.06"
.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>
.P
.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
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.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 .
.P
If
.I x
is a NaN, a NaN is returned, and
.I *iptr
is set to a NaN.
.P
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).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR modf (),
.BR modff (),
.BR modfl ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
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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