CMake/Tests/Tutorial/Step5/MathFunctions/mysqrt.cxx

41 lines
765 B
C++
Raw Normal View History

2005-11-10 18:51:25 +03:00
#include "MathFunctions.h"
#include "TutorialConfig.h"
#include <stdio.h>
2005-11-10 18:51:25 +03:00
// include the generated table
#include "Table.h"
#include <math.h>
// a hack square root calculation using simple operations
double mysqrt(double x)
{
if (x <= 0) {
2005-11-10 18:51:25 +03:00
return 0;
}
2005-11-10 18:51:25 +03:00
double result;
// if we have both log and exp then use them
double delta;
2005-11-10 18:51:25 +03:00
// use the table to help find an initial value
result = x;
if (x >= 1 && x < 10) {
2005-11-10 18:51:25 +03:00
result = sqrtTable[static_cast<int>(x)];
}
2005-11-10 18:51:25 +03:00
// do ten iterations
int i;
for (i = 0; i < 10; ++i) {
if (result <= 0) {
2005-11-10 18:51:25 +03:00
result = 0.1;
}
delta = x - (result * result);
result = result + 0.5 * delta / result;
fprintf(stdout, "Computing sqrt of %g to be %g\n", x, result);
}
2005-11-10 18:51:25 +03:00
return result;
}