It looks like somewhere else in your program (or a type signature
somewhere) is trying to force the result of sqrt to be an Int which
won't work since square roots are irrational (represented by the
computer as a Float or Double).
You might try (1) making sure the place where distBetween is used
isn't trying to use only Ints or Integers and (2) taking off explicit
type signatures and seeing if that works (the compiler can usually get
things working for you as long as you don't give it misinformation in
type signatures). Also, a more useful type of Point if you are taking
distances would be
type Point = (Float,Float)
instead (or you can leave that out because the function type for
distBetween will be inferred to be the "right thing", i.e.
(Float,Float) is already a valid type without needing to be named).
Hope that helps,
Jared.
--
http://www.updike.org/~jared/
reverse ")-:"
On 4/27/06, Aditya Siram
Hi all, I just started working with Haskell and am having some difficulties with its type system. Here is function that is supposed to calculate the distance between two coordinates: distBetween (x1,y1) (x2,y2) = sqrt((x2-x1)^2 + (y2-y1)^2)
I am trying to explictly give it a type signature. Here is what I have tried and the errors generated by Hugs:
type Point = (Int,Int) distBetween :: Point -> Point -> Float
ERROR - Type error in explicitly typed binding *** Term : distBetween *** Type : Point -> Point -> Int *** Does not match : Point -> Point -> Float
distBetween :: Point -> Point -> Int
Instance of Floating Int required for definition of distBetween
Any help is appreciated... Deech
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