MODF(3)                    POSIX Programmer's Manual                   MODF(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 .



IEEE/The Open Group                  2017                              MODF(3)
