Function to find the nth digit of Pi

Question

I have always wanted to find an algorithm that did this. I do not care how slow it is, just as long as it can return the nth digit of Pi:

ex:

size_t piAt(long long int n)
{
}

Preferably, not using an infinite series.

If anyone has a function or class that does this, in C or C++ I'd really be interested in seeing it.

Thanks