Am 06/16/2014 09:28 PM, schrieb Miguel Mitrofanov:
Now, you can just as easy implement all that without classes:
data AppendNumber a = AppendNumber {appendNumber :: a -> Integer -> a} appendNumberInteger :: AppendNumber Integer appendNumberInteger = AppendNumber {appendNumber = \n d -> n + d} appendNumberString :: AppendNumber String appendNumberString = AppendNumber {appendNumber = \s d -> s ++ show d} increment :: AppendNumber a -> a -> a increment an n = appendNumber an n 1 main = print $ increment appendNumberInteger 2048
I just stumbled across some other things: When I use classes I can implement one function in terms of another function of the same class. When I use data/newtype I can't seem to do this. So I can replace a class by a data/newtype only when it wraps around a single function. Also I can use as many parameters as I like in data/newtype, but not in classes (if I stick to standard haskell) Is this correct?