1ISLESS(3P)                 POSIX Programmer's Manual                ISLESS(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       isless — test if x is less than y
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SYNOPSIS

15       #include <math.h>
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17       int isless(real-floating x, real-floating y);
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DESCRIPTION

20       The functionality described on this reference page is aligned with  the
21       ISO C  standard.  Any  conflict between the requirements described here
22       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
23       defers to the ISO C standard.
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25       The  isless()  macro shall determine whether its first argument is less
26       than its second argument. The value of isless(x, y) shall be  equal  to
27       (x) < (y);  however, unlike (x) < (y), isless(x, y) shall not raise the
28       invalid floating-point exception when x and y are unordered.
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RETURN VALUE

31       Upon successful completion, the isless() macro shall return  the  value
32       of (x) < (y).
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34       If x or y is NaN, 0 shall be returned.
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ERRORS

37       No errors are defined.
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39       The following sections are informative.
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EXAMPLES

42       None.
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APPLICATION USAGE

45       The  relational  and  equality operators support the usual mathematical
46       relationships between numeric values. For any ordered pair  of  numeric
47       values,  exactly one of the relationships (less, greater, and equal) is
48       true. Relational operators may raise the invalid floating-point  excep‐
49       tion  when  argument values are NaNs. For a NaN and a numeric value, or
50       for two NaNs, just the unordered relationship is true. This macro is  a
51       quiet  (non-floating-point  exception  raising) version of a relational
52       operator. It facilitates writing efficient code that accounts for  NaNs
53       without suffering the invalid floating-point exception. In the SYNOPSIS
54       section, real-floating indicates that the argument shall be an  expres‐
55       sion of real-floating type.
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RATIONALE

58       None.
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FUTURE DIRECTIONS

61       None.
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SEE ALSO

64       isgreater(),    isgreaterequal(),    islessequal(),    islessgreater(),
65       isunordered()
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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                           ISLESS(3P)
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