CMakeLua/Tests/Tutorial/Step6/MathFunctions/mysqrt.cxx

   1 #include <stdio.h>
   2 #include "MathFunctions.h"
   3 #include "TutorialConfig.h"
   4
   5 // include the generated table
   6 #include "Table.h"
   7
   8 #include <math.h>
   9
  10 // a hack square root calculation using simple operations
  11 double mysqrt(double x)
  12 {
  13   if (x <= 0)
  14     {
  15     return 0;
  16     }
  17
  18   double result;
  19
  20   // if we have both log and exp then use them
  21   double delta;
  22
  23   // use the table to help find an initial value
  24   result = x;
  25   if (x >= 1 && x < 10)
  26     {
  27     result = sqrtTable[static_cast<int>(x)];
  28     }
  29
  30   // do ten iterations
  31   int i;
  32   for (i = 0; i < 10; ++i)
  33     {
  34     if (result <= 0)
  35       {
  36       result = 0.1;
  37       }
  38     delta = x - (result*result);
  39     result = result + 0.5*delta/result;
  40     fprintf(stdout,"Computing sqrt of %g to be %g\n",x,result);
  41     }
  42
  43   return result;
  44 }