Implementation error

I think the sign for this function may be inverted. Compare the graph with the wiki page: http://en.wikipedia.org/wiki/Fresnel_integral

In the code, the sign variable is being calculated incorrectly. Replacing

int sign = 2*(x<0) - 1;

with something like

const int sign = x > 0 ? +1 : -1;

should fix it.

The same thing applies to the cosine equivalent.