On Sun, Nov 26, 2017 at 02:50:30PM +0100, Patrik Iselind wrote:
Hi,
What's the difference between `delta :: (Point t) => t -> t -> Double` and `delta :: Point p -> Point q -> Double`. The later one is accepted by GHCI when i do :load.
Hello Patrik, `delta :: (Point t) => t -> t -> Double` means Point is a typeclass and t is an instance of a typeclass. In your case point is a datatype (data Point a etc. etc.) so the second signature is the correct one.
In the second version, which is accepted by GHCI, i don't see the point of p and q. Can i use these somehow?
`p` and `q` are the parameter of `Point a`, but since the definition of Point is: data Point a = Coordinate Double Double deriving (Show) that `a` most likely has... no point (ueueuee pardon the pun) and would better be written as data Point = Coordinate Double Double deriving (Show) Does this make sense?