[Haskell-cafe] Type conversion problems

Christian Hofer Christian.Hofer at gmx.de
Sun Jun 13 05:15:28 EDT 2004


after some playing around with monad transformers and starting to like 
those specialities of Haskell, I am currently really feeling thrown 
back by a simple problem: trying to write a sine-function...

Here is the part of my code that is troubling me:

fac :: Integer -> Integer
fac n = product [1..n]

term :: Double -> Integer -> Double
term x n = (-1.0::Double)**(fromInteger n) * (x**(fromInteger (2*n + 
1))) /
	   (fromInteger (fac (2*n + 1)))

The term function is supposed to be the direct translation of the 
formula of a term within the sum. But it isn't: it is actually 
cluttered with lots of type conversions, and I had a hard time figuring 
out how to make it work at all. I hope that this is not the easiest way 
to do that and I would appreciate any help on how to handle those type 
conversion issues...


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