Fast Reduced Fractions...

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Fast Reduced Fractions...

Hello, I'm currently hunting for a way to generate a reduced fraction from
a decimal using C (the language doesn't matter, I'm after a formula).  I've
found a solution, but as you will see, it is not pretty with large values
for the numerator and denominator:

int x, y;
double MyDec = 99999998/99999999;

y = 2;
x = 1;
while(abs((double)x/(double)y - MyDec) > .00000000000001)
{
  x++;
  if (x == y)
  {
    x = 1;
    y++;
  }
}
printf("%i/%i\n", x, y);

Yes, it should work (untested and for good reason)...but with the above
MyDec value it will take a *LOOONG* time to process (and might print a
close but wrong answer).  What I want is a formula to calculate a correct
reduced fraction from a decimal in a single pass without the absolute value
and comparison (I could optimize the above code, but I really want a single
pass formula).

Any suggestions?  I'm going to go look through some ancient math books
tomorrow, but I thought I would throw the question out tonight so all of
you could chew on it for a while.


           Thomas J. Hruska -- shinelight@crosswinds.net
Shining Light Productions -- "Meeting the needs of fellow programmers"
                  http://www.shininglightpro.com/

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