1FMOD(3P)                   POSIX Programmer's Manual                  FMOD(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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11

NAME

13       fmod, fmodf, fmodl — floating-point remainder value function
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SYNOPSIS

16       #include <math.h>
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18       double fmod(double x, double y);
19       float fmodf(float x, float y);
20       long double fmodl(long double x, long double y);
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DESCRIPTION

23       The functionality described on this reference page is aligned with  the
24       ISO C  standard.  Any  conflict between the requirements described here
25       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
26       defers to the ISO C standard.
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28       These  functions shall return the floating-point remainder of the divi‐
29       sion of x by y.
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31       An application wishing to check for error situations should  set  errno
32       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
33       functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
34       FE_DIVBYZERO  |  FE_OVERFLOW  | FE_UNDERFLOW) is non-zero, an error has
35       occurred.
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RETURN VALUE

38       These functions shall return the value x−i*y, for some integer  i  such
39       that, if y is non-zero, the result has the same sign as x and magnitude
40       less than the magnitude of y.
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42       If the correct value would cause underflow, and is not representable, a
43       range  error  may  occur,  and fmod(), modf(), and fmodl() shall return
44       0.0, or (if the IEC 60559 Floating-Point option is  not  supported)  an
45       implementation-defined  value  no  greater  in  magnitude than DBL_MIN,
46       FLT_MIN, and LDBL_MIN, respectively.
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48       If x or y is NaN, a NaN shall be returned.
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50       If y is zero, a domain error shall occur, and a NaN shall be returned.
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52       If x is infinite, a domain error  shall  occur,  and  a  NaN  shall  be
53       returned.
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55       If x is ±0 and y is not zero, ±0 shall be returned.
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57       If x is not infinite and y is ±Inf, x shall be returned.
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59       If  the  correct  value  would cause underflow, and is representable, a
60       range error may occur and the correct value shall be returned.
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ERRORS

63       These functions shall fail if:
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65       Domain Error
66                   The x argument is infinite or y is zero.
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68                   If the integer expression (math_errhandling  &  MATH_ERRNO)
69                   is  non-zero,  then  errno  shall be set to [EDOM].  If the
70                   integer expression (math_errhandling &  MATH_ERREXCEPT)  is
71                   non-zero,  then  the invalid floating-point exception shall
72                   be raised.
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74       These functions may fail if:
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76       Range Error The result underflows.
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78                   If the integer expression (math_errhandling  &  MATH_ERRNO)
79                   is  non-zero,  then errno shall be set to [ERANGE].  If the
80                   integer expression (math_errhandling &  MATH_ERREXCEPT)  is
81                   non-zero, then the underflow floating-point exception shall
82                   be raised.
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84       The following sections are informative.
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EXAMPLES

87       None.
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APPLICATION USAGE

90       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
91       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
92       at least one of them must be non-zero.
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RATIONALE

95       None.
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FUTURE DIRECTIONS

98       None.
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SEE ALSO

101       feclearexcept(), fetestexcept(), isnan()
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103       Section 4.19, Treatment of Error Conditions for Mathematical Functions,
104       <math.h>
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107       Portions  of  this text are reprinted and reproduced in electronic form
108       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
109       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
110       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
111       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
112       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
113       event of any discrepancy between this version and the original IEEE and
114       The Open Group Standard, the original IEEE and The Open Group  Standard
115       is  the  referee document. The original Standard can be obtained online
116       at http://www.unix.org/online.html .
117
118       Any typographical or formatting errors that appear  in  this  page  are
119       most likely to have been introduced during the conversion of the source
120       files to man page format. To report such errors,  see  https://www.ker‐
121       nel.org/doc/man-pages/reporting_bugs.html .
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125IEEE/The Open Group                  2013                             FMOD(3P)
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