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


NAME
       isless — test if x is less than y


SYNOPSIS
       #include <math.h>

       int isless(real-floating x, real-floating y);


DESCRIPTION
       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2008 defers to the ISO C standard.

       The isless() macro shall determine whether its first argument is less than its second argument. The value
       of isless(x, y) shall be equal to (x) < (y); however, unlike (x) < (y), isless(x, y) shall not raise  the
       invalid floating-point exception when x and y are unordered.


RETURN VALUE
       Upon successful completion, the isless() macro shall return the value of (x) < (y).

       If x or y is NaN, 0 shall be returned.


ERRORS
       No errors are defined.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       The  relational  and  equality  operators  support  the  usual mathematical relationships between numeric
       values. For any ordered pair of numeric values, exactly one of  the  relationships  (less,  greater,  and
       equal)  is true. Relational operators may raise the invalid floating-point exception when argument values
       are NaNs. For a NaN and a numeric value, or for two NaNs, just the unordered relationship is  true.  This
       macro  is a quiet (non-floating-point exception raising) version of a relational operator. It facilitates
       writing efficient code that accounts for NaNs without suffering the invalid floating-point exception.  In
       the  SYNOPSIS  section, real-floating indicates that the argument shall be an expression of real-floating
       type.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       isgreater(), isgreaterequal(), islessequal(), islessgreater(), isunordered()

       The Base Definitions volume of POSIX.1‐2008, <math.h>


COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers,  Inc
       and  The  Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event
       of any discrepancy between this version and the original IEEE and The Open Group Standard,  the  original
       IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at
       http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .