1ISGREATER(3)               Linux Programmer's Manual              ISGREATER(3)
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NAME

6       isgreater,    isgreaterequal,   isless,   islessequal,   islessgreater,
7       isunordered - floating-point relational tests without exception for NaN
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SYNOPSIS

10       #include <math.h>
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12       int isgreater(x, y);
13       int isgreaterequal(x, y);
14       int isless(x, y);
15       int islessequal(x, y);
16       int islessgreater(x, y);
17       int isunordered(x, y);
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19       Link with -lm.
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21   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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23           All functions described here:
24               _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
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DESCRIPTION

27       The normal relational operations (like <, "less than") fail if  one  of
28       the operands is NaN.  This will cause an exception.  To avoid this, C99
29       defines the macros listed below.
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31       These macros are guaranteed to evaluate their arguments only once.  The
32       arguments  must be of real floating-point type (note: do not pass inte‐
33       ger values as arguments to these macros, since the arguments  will  not
34       be promoted to real-floating types).
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36       isgreater()
37              determines (x) > (y) without an exception if x or y is NaN.
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39       isgreaterequal()
40              determines (x) >= (y) without an exception if x or y is NaN.
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42       isless()
43              determines (x) < (y) without an exception if x or y is NaN.
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45       islessequal()
46              determines (x) <= (y) without an exception if x or y is NaN.
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48       islessgreater()
49              determines (x) < (y) || (x) > (y) without an exception if x or y
50              is NaN.  This macro is not equivalent to x != y because that ex‐
51              pression is true if x or y is NaN.
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53       isunordered()
54              determines whether its arguments are unordered, that is, whether
55              at least one of the arguments is a NaN.
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RETURN VALUE

58       The macros other than isunordered() return the result of the relational
59       comparison; these macros return 0 if either argument is a NaN.
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61       isunordered() returns 1 if x or y is NaN and 0 otherwise.
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ERRORS

64       No errors occur.
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ATTRIBUTES

67       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
68       tributes(7).
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70       ┌────────────────────────────────────────────┬───────────────┬─────────┐
71       │Interface                                   │ Attribute     │ Value   │
72       ├────────────────────────────────────────────┼───────────────┼─────────┤
73       │isgreater(), isgreaterequal(), isless(),    │ Thread safety │ MT-Safe │
74       │islessequal(), islessgreater(),             │               │         │
75       │isunordered()                               │               │         │
76       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

79       POSIX.1-2001, POSIX.1-2008, C99.
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NOTES

82       Not all hardware supports these functions, and where  hardware  support
83       isn't provided, they will be emulated by macros.  This will result in a
84       performance penalty.  Don't use these functions if NaN is of no concern
85       for you.
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SEE ALSO

88       fpclassify(3), isnan(3)
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COLOPHON

91       This  page  is  part of release 5.12 of the Linux man-pages project.  A
92       description of the project, information about reporting bugs,  and  the
93       latest     version     of     this    page,    can    be    found    at
94       https://www.kernel.org/doc/man-pages/.
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98                                  2021-03-22                      ISGREATER(3)
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