'\" et
.TH MODF "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.

.SH NAME
modf,
modff,
modfl
\(em decompose a floating-point number
.SH SYNOPSIS
.LP
.nf
#include <math.h>
.P
double modf(double \fIx\fP, double *\fIiptr\fP);
float modff(float \fIvalue\fP, float *\fIiptr\fP);
long double modfl(long double \fIvalue\fP, long double *\fIiptr\fP);
.fi
.SH DESCRIPTION
The functionality described on this reference page is aligned with the
ISO\ C standard. Any conflict between the requirements described here and the
ISO\ C standard is unintentional. This volume of POSIX.1\(hy2008 defers to the ISO\ C standard.
.P
These functions shall break the argument
.IR x
into integral and fractional parts, each of which has the same sign as
the argument. It stores the integral part as a
.BR double
(for the
\fImodf\fR()
function), a
.BR float
(for the
\fImodff\fR()
function), or a
.BR "long double"
(for the
\fImodfl\fR()
function), in the object pointed to by
.IR iptr .
.SH "RETURN VALUE"
Upon successful completion, these functions shall return the signed
fractional part of
.IR x .
.P
If
.IR x
is NaN, a NaN shall be returned, and *\fIiptr\fP shall be set to a
NaN.
.P
If
.IR x
is \(+-Inf, \(+-0 shall be returned, and *\fIiptr\fP shall be set to
\(+-Inf.
.SH ERRORS
No errors are defined.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
The
\fImodf\fR()
function computes the function result and *\fIiptr\fP such that:
.sp
.RS 4
.nf
\fB
a = modf(x, iptr) ;
x == a+*iptr ;
.fi \fR
.P
.RE
.P
allowing for the usual floating-point inaccuracies.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIfrexp\fR\^(\|)",
.IR "\fIisnan\fR\^(\|)",
.IR "\fIldexp\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "\fB<math.h>\fP"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.unix.org/online.html .

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