allowing users access to a trusted C function

I created (as a superuser) a set of C functions to handle boolean
arithmetic (has to do with simplifying search queries of mine). I would
like users to be able to access those functions somehow. They are very
simple functions so I can't imagine they would be exploited (unless I am
missing something). Is this possible? Otherwise I could use PL/pgSQL,
but I assume that would be significantly slower for a mathematical
operation.

Thanks,
    Jeff Davis