1MODF(3P)                   POSIX Programmer's Manual                  MODF(3P)
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PROLOG

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

12       modf, modff, modfl — decompose a floating-point number
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SYNOPSIS

15       #include <math.h>
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17       double modf(double x, double *iptr);
18       float modff(float value, float *iptr);
19       long double modfl(long double value, long double *iptr);
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DESCRIPTION

22       The functionality described on this reference page is aligned with  the
23       ISO C  standard.  Any  conflict between the requirements described here
24       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
25       defers to the ISO C standard.
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27       These functions shall break the argument x into integral and fractional
28       parts, each of which has the same sign as the argument. It  stores  the
29       integral  part  as a double (for the modf() function), a float (for the
30       modff() function), or a long double (for the modfl() function), in  the
31       object pointed to by iptr.
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RETURN VALUE

34       Upon  successful  completion,  these  functions shall return the signed
35       fractional part of x.
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37       If x is NaN, a NaN shall be returned, and *iptr shall be set to a NaN.
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39       If x is ±Inf, ±0 shall be returned, and *iptr shall be set to ±Inf.
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ERRORS

42       No errors are defined.
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44       The following sections are informative.
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EXAMPLES

47       None.
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APPLICATION USAGE

50       The modf() function computes the function result and *iptr such that:
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53           a = modf(x, iptr) ;
54           x == a+*iptr ;
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56       allowing for the usual floating-point inaccuracies.
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RATIONALE

59       None.
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FUTURE DIRECTIONS

62       None.
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SEE ALSO

65       frexp(), isnan(), ldexp()
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67       The Base Definitions volume of POSIX.1‐2017, <math.h>
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70       Portions of this text are reprinted and reproduced in  electronic  form
71       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
72       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
73       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
74       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
75       event of any discrepancy between this version and the original IEEE and
76       The Open Group Standard, the original IEEE and The Open Group  Standard
77       is  the  referee document. The original Standard can be obtained online
78       at http://www.opengroup.org/unix/online.html .
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80       Any typographical or formatting errors that appear  in  this  page  are
81       most likely to have been introduced during the conversion of the source
82       files to man page format. To report such errors,  see  https://www.ker‐
83       nel.org/doc/man-pages/reporting_bugs.html .
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87IEEE/The Open Group                  2017                             MODF(3P)
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