problems with Haskell's Number Types
- by mindeavor.
I have the following haskell code:
fac n = product [1..n]
taylor3s w0 f f' f'' t h = w1 : taylor3s w1 f f' f'' (t+h) h
where hp i = h^i / fac i
w1 = w0 + (hp 1) * f t w0 + (hp 2) * f' t w0 + (hp 3) * f'' t w0
taylor_results = take 4 $ taylor3s 1 f f' f'' 1 0.25
where f t x = t^4 - 4*x/t
f' t x = 4*t^3 - 4*(f t x)/t + 4*x/t^2
f'' t x = 12*t^2 - 4*(f' t x)/t + 8*(f t x)/t^2 - 8*x/t^3
taylor_results is supposed to be a use case of taylor3s. However, there is something wrong with the number type inferencing. When I try to compile, this is the error I get:
practice.hs:93:26:
Ambiguous type variable `a' in the constraints:
`Integral a'
arising from a use of `taylor3s' at practice.hs:93:26-51
`Fractional a' arising from a use of `f' at practice.hs:93:37
Possible cause: the monomorphism restriction applied to the following:
taylor_results :: [a] (bound at practice.hs:93:0)
Probable fix: give these definition(s) an explicit type signature
or use -XNoMonomorphismRestriction
Can someone help me with understanding what the problem is?
