external/io_grib1/WGRIB/intpower.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3
   4 /*
   5  * w. ebisuzaki
   6  *
   7  *  return x**y
   8  *
   9  *
  10  *  input: double x
  11  *         int y
  12  */
  13 double int_power(double x, int y) {
  14
  15         double value;
  16
  17         if (y < 0) {
  18                 y = -y;
  19                 x = 1.0 / x;
  20         }
  21         value = 1.0;
  22
  23         while (y) {
  24                 if (y & 1) {
  25                         value *= x;
  26                 }
  27                 x = x * x;
  28                 y >>= 1;
  29         }
  30         return value;
  31 }