man3/fpclassify.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\" Distributed under GPL, 2002-07-27 Walter Harms
   3 .\" This was done with the help of the glibc manual.
   4 .\"
   5 .\" 2004-10-31, aeb, corrected
   6 .TH fpclassify 3  2004-10-31 "" "Linux Programmer's Manual"
   7 .SH NAME
   8 fpclassify, isfinite, isnormal, isnan \- floating-point classification macros
   9 .SH SYNOPSIS
  10 .nf
  11 .B #include <math.h>
  12 .sp
  13 .BI "int fpclassify(" x );
  14 .sp
  15 .BI "int isfinite(" x );
  16 .sp
  17 .BI "int isnormal(" x );
  18 .sp
  19 .BI "int isnan(" x );
  20 .sp
  21 .BI "int isinf(" x );
  22 .fi
  23 .sp
  24 Compile with -std=c99; link with \-lm.
  25 .SH DESCRIPTION
  26 Floating point numbers can have special values, such as
  27 infinite or NaN. With the macro
  28 .BI fpclassify( x )
  29 you can find out what type
  30 .I x
  31 is. The macro takes any floating-point expression as argument.
  32 The result takes one of the following values:
  33 .TP
  34 FP_NAN
  35 .I x
  36 is "Not a Number".
  37 .TP
  38 FP_INFINITE
  39 .I x
  40 is either plus or minus infinity.
  41 .TP
  42 FP_ZERO
  43 .I x
  44 is zero.
  45 .TP
  46 FP_SUBNORMAL
  47 .I x
  48 is too small to be represented in normalized format.
  49 .TP
  50 FP_NORMAL
  51 if nothing of the above is correct that it must be a
  52 normal floating-point number.
  53 .LP
  54 The other macros provide a short answer to some standard questions.
  55 .TP
  56 .BI isfinite( x )
  57 returns a non-zero value if
  58 .br
  59 (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
  60 .TP
  61 .BI isnormal( x )
  62 returns a non-zero value if
  63 (fpclassify(x) == FP_NORMAL)
  64 .TP
  65 .BI isnan( x )
  66 returns a non-zero value if
  67 (fpclassify(x) == FP_NAN)
  68 .TP
  69 .BI isinf( x )
  70 returns a non-zero value if
  71 (fpclassify(x) == FP_INFINITE)
  72 .SH NOTE
  73 On systems conforming to BSD 4.3,
  74 .B isinf()
  75 will return 1 for positive, and \-1 for negative infinity.
  76 .SH "CONFORMING TO"
  77 C99
  78 .SH "SEE ALSO"
  79 .BR finite (3),
  80 .BR INFINITY (3),
  81 .BR isgreater (3)
  82