using the exp() function in math.h

Hi folks. I'm new to using C and the math functions, and am having some trouble with the exp() function. I have a statement in my arduino program like this:

K = 1 - exp(-2piC/S);

where K is a double, and pi, C, and S are defined elsewhere and are floats. Unfortunately no matter what values I use for C and S for some reason K always comes out as 0. Even when I do something like:

double stuff = -2piC/S;
K = 1 - exp(stuff);

I still have the same problem. Does anyone have any ideas? Thanks in advance!

Nevermind - I figured out what was going on. I was using serial.print to check the value of K, and I noticed when checking the page on floating point integers that serial.print throws out the fractional part when printing to the serial port. The values I had the constants set to in the equation above happened to come out to 0.443, so serial.print was returning 0 for K. So uhm, there ya go.