Sinc function
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The sinc function, , is a useful function that is a little tricky to implement because it becomes as x approaches . 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 | (abs x) >= taylor_n_bound = (sin x)/x
| otherwise = 1 - (x^2/6) + (x^4/120)
where
taylor_n_bound = sqrt $ sqrt epsilon