Sinc function
From HaskellWiki
The sinc function, 
, is a useful function that is a little tricky to implement because it becomes 
as x approaches 0. Here is an implementation taken from the Boost library.
epsilon :: RealFloat a => a epsilon = encodeFloat 1 (fromIntegral $ 1-floatDigits epsilon) {- Boosted from Boost http://www.boost.org/boost/math/special_functions/sinc.hpp -} sinc :: (RealFloat a) => a -> a sinc x = if abs x >= taylor_n_bound then sin x / x else 1 - x^2/6 + x^4/120 where taylor_n_bound = sqrt $ sqrt epsilon
