man3/isgreater.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\"
   3 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   4 .\" Distributed under GPL
   5 .\" %%%LICENSE_END
   6 .\"
   7 .\" 2002-07-27 Walter Harms
   8 .\" this was done with the help of the glibc manual
   9 .\"
  10 .TH ISGREATER 3  2017-09-15 "" "Linux Programmer's Manual"
  11 .SH NAME
  12 isgreater, isgreaterequal, isless, islessequal, islessgreater,
  13 isunordered \- floating-point relational tests without exception for NaN
  14 .SH SYNOPSIS
  15 .nf
  16 .B #include <math.h>
  17 .PP
  18 .BI "int isgreater(" x ", " y );
  19 .PP
  20 .BI "int isgreaterequal(" x ", " y );
  21 .PP
  22 .BI "int isless(" x ", " y );
  23 .PP
  24 .BI "int islessequal(" x ", " y );
  25 .PP
  26 .BI "int islessgreater(" x ", " y );
  27 .PP
  28 .BI "int isunordered(" x ", " y );
  29 .fi
  30 .PP
  31 Link with \fI\-lm\fP.
  32 .PP
  33 .in -4n
  34 Feature Test Macro Requirements for glibc (see
  35 .BR feature_test_macros (7)):
  36 .in
  37 .PP
  38 .ad l
  39 All functions described here:
  40 .RS
  41 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  42 .RE
  43 .ad b
  44 .SH DESCRIPTION
  45 The normal relational operations (like
  46 .BR < ,
  47 "less than")
  48 fail if one of the operands is NaN.
  49 This will cause an exception.
  50 To avoid this, C99 defines the macros listed below.
  51 .PP
  52 These macros are guaranteed to evaluate their arguments only once.
  53 The arguments must be of real floating-point type (note: do not pass
  54 integer values as arguments to these macros, since the arguments will
  55 .I not
  56 be promoted to real-floating types).
  57 .TP
  58 .BR isgreater ()
  59 determines \fI(x)\ >\ (y)\fP without an exception
  60 if
  61 .IR x
  62 or
  63 .I y
  64 is NaN.
  65 .TP
  66 .BR isgreaterequal ()
  67 determines \fI(x)\ >=\ (y)\fP without an exception
  68 if
  69 .IR x
  70 or
  71 .I y
  72 is NaN.
  73 .TP
  74 .BR isless ()
  75 determines \fI(x)\ <\ (y)\fP without an exception
  76 if
  77 .IR x
  78 or
  79 .I y
  80 is NaN.
  81 .TP
  82 .BR islessequal ()
  83 determines \fI(x)\ <=\ (y)\fP without an exception
  84 if
  85 .IR x
  86 or
  87 .I y
  88 is NaN.
  89 .TP
  90 .BR islessgreater ()
  91 determines \fI(x)\ < (y) || (x) >\ (y)\fP
  92 without an exception if
  93 .IR x
  94 or
  95 .I y
  96 is NaN.
  97 This macro is not equivalent to \fIx\ !=\ y\fP because that expression is
  98 true if
  99 .IR x
 100 or
 101 .I y
 102 is NaN.
 103 .TP
 104 .BR isunordered ()
 105 determines whether its arguments are unordered, that is, whether
 106 at least one of the arguments is a NaN.
 107 .SH RETURN VALUE
 108 The macros other than
 109 .BR isunordered ()
 110 return the result of the relational comparison;
 111 these macros return 0 if either argument is a NaN.
 112 .PP
 113 .BR isunordered ()
 114 returns 1 if
 115 .IR x
 116 or
 117 .I y
 118 is NaN and 0 otherwise.
 119 .SH ERRORS
 120 No errors occur.
 121 .SH ATTRIBUTES
 122 For an explanation of the terms used in this section, see
 123 .BR attributes (7).
 124 .ad l
 125 .TS
 126 allbox;
 127 lbw30 lb lb
 128 l l l.
 129 Interface       Attribute       Value
 130 T{
 131 .BR isgreater (),
 132 .BR isgreaterequal (),
 133 .BR isless (),
 134 .BR islessequal (),
 135 .BR islessgreater (),
 136 .BR isunordered ()
 137 T}      Thread safety   MT-Safe
 138 .TE
 139 .ad
 140 .SH CONFORMING TO
 141 POSIX.1-2001, POSIX.1-2008, C99.
 142 .SH NOTES
 143 Not all hardware supports these functions,
 144 and where hardware support isn't provided, they will be emulated by macros.
 145 This will result in a performance penalty.
 146 Don't use these functions if NaN is of no concern for you.
 147 .SH SEE ALSO
 148 .BR fpclassify (3),
 149 .BR isnan (3)