MODF

Section: POSIX Programmer's Manual (3P)
Updated: 2017
Index Return to Main Contents
 

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.  

NAME

modf, modff, modfl --- decompose a floating-point number  

SYNOPSIS

#include <math.h>

double modf(double x, double *iptr);
float modff(float value, float *iptr);
long double modfl(long double value, long double *iptr);
 

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.1-2017 defers to the ISO C standard.

These functions shall break the argument x into integral and fractional parts, each of which has the same sign as the argument. It stores the integral part as a double (for the modf() function), a float (for the modff() function), or a long double (for the modfl() function), in the object pointed to by iptr.  

RETURN VALUE

Upon successful completion, these functions shall return the signed fractional part of x.

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

If x is ±Inf, ±0 shall be returned, and *iptr shall be set to ±Inf.  

ERRORS

No errors are defined.

The following sections are informative.  

EXAMPLES

None.  

APPLICATION USAGE

The modf() function computes the function result and *iptr such that:


a = modf(x, iptr) ;
x == a+*iptr ;

allowing for the usual floating-point inaccuracies.  

RATIONALE

None.  

FUTURE DIRECTIONS

None.  

SEE ALSO

frexp(), isnan(), ldexp()

The Base Definitions volume of POSIX.1-2017, <math.h>  

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .


 

Index

PROLOG
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
EXAMPLES
APPLICATION USAGE
RATIONALE
FUTURE DIRECTIONS
SEE ALSO
COPYRIGHT

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