missing/isinf.c

DEFINITIONS

1. isinf
2. zero
3. one
4. inf
5. isinf

   1  /* public domain rewrite of isinf(3) */
   2  
   3  #ifdef __osf__
   4  
   5  #define _IEEE 1
   6  #include <nan.h>
   7  
   8  int
isinf(n)
  10      double n;
  11  {
  12          if (IsNANorINF(n) && IsINF(n)) {
  13                  return 1;
  14          } else {
  15                  return 0;
  16          }
  17  }
  18  
  19  #else
  20  
  21  #include "config.h"
  22  #ifdef HAVE_STRING_H
  23  # include <string.h>
  24  #else
  25  # include <strings.h>
  26  #endif
  27  
  28  static double zero()    { return 0.0; }
  29  static double one()     { return 1.0; }
  30  static double inf()     { return one() / zero(); }
  31  
  32  int
isinf(n)
  34      double n;
  35  {
  36      static double pinf = 0.0;
  37      static double ninf = 0.0;
  38  
  39      if (pinf == 0.0) {
  40          pinf = inf();
  41          ninf = -pinf;
  42      }
  43      return memcmp(&n, &pinf, sizeof n) == 0
  44          || memcmp(&n, &ninf, sizeof n) == 0;
  45  }
  46  #endif