drem(3) - f38

1remainder(3)               Library Functions Manual               remainder(3)
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NAME

6       drem,  dremf, dreml, remainder, remainderf, remainderl - floating-point
7       remainder function
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LIBRARY

10       Math library (libm, -lm)
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SYNOPSIS

13       #include <math.h>
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15       double remainder(double x, double y);
16       float remainderf(float x, float y);
17       long double remainderl(long double x, long double y);
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19       /* Obsolete synonyms */
20       [[deprecated]] double drem(double x, double y);
21       [[deprecated]] float dremf(float x, float y);
22       [[deprecated]] long double dreml(long double x, long double y);
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24   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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26       remainder():
27           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
28               || _XOPEN_SOURCE >= 500
29               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
30               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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32       remainderf(), remainderl():
33           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
34               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
35               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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37       drem(), dremf(), dreml():
38           /* Since glibc 2.19: */ _DEFAULT_SOURCE
39               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

42       These functions compute the remainder of dividing x by y.   The  return
43       value  is x-n*y, where n is the value x / y, rounded to the nearest in‐
44       teger.  If the absolute value of x-n*y is 0.5, n is chosen to be even.
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46       These functions are  unaffected  by  the  current  rounding  mode  (see
47       fenv(3)).
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49       The drem() function does precisely the same thing.
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RETURN VALUE

52       On success, these functions return the floating-point remainder, x-n*y.
53       If the return value is 0, it has the sign of x.
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55       If x or y is a NaN, a NaN is returned.
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57       If x is an infinity, and y is not a NaN, a domain error occurs,  and  a
58       NaN is returned.
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60       If  y  is zero, and x is not a NaN, a domain error occurs, and a NaN is
61       returned.
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ERRORS

64       See math_error(7) for information on how to determine whether an  error
65       has occurred when calling these functions.
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67       The following errors can occur:
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69       Domain error: x is an infinity and y is not a NaN
70              errno  is set to EDOM (but see BUGS).  An invalid floating-point
71              exception (FE_INVALID) is raised.
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73              These functions do not set errno for this case.
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75       Domain error: y is zero
76              errno is set  to  EDOM.   An  invalid  floating-point  exception
77              (FE_INVALID) is raised.
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ATTRIBUTES

80       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
81       tributes(7).
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83       ┌────────────────────────────────────────────┬───────────────┬─────────┐
84       │Interface                                   │ Attribute     │ Value   │
85       ├────────────────────────────────────────────┼───────────────┼─────────┤
86       │drem(), dremf(), dreml(), remainder(),      │ Thread safety │ MT-Safe │
87       │remainderf(), remainderl()                  │               │         │
88       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

91       remainder()
92       remainderf()
93       remainderl()
94              C11, POSIX.1-2008.
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96       drem()
97       dremf()
98       dreml()
99              None.
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HISTORY

102       remainder()
103       remainderf()
104       remainderl()
105              C99, POSIX.1-2001.
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107       drem() 4.3BSD.
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109       dremf()
110       dreml()
111              Tru64, glibc2.
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BUGS

114       Before glibc 2.15, the call
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116           remainder(nan(""), 0);
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118       returned  a NaN, as expected, but wrongly caused a domain error.  Since
119       glibc 2.15, a silent NaN (i.e., no domain error) is returned.
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121       Before glibc 2.15, errno was not set to EDOM for the domain error  that
122       occurs when x is an infinity and y is not a NaN.
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EXAMPLES

125       The call "remainder(29.0, 3.0)" returns -1.
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