"S. Alexander Jacobson" wrote:
Does anyone know why the haskell designers did not make the syntax right associative? It would clean up a lot of stuff.
Haskell Non-Haskell Left Associative Right Associative foo (bar (baz (x))) foo bar baz x foo $ bar $ baz x foo bar baz x add (square x) (square y) add square x square y add (square x) y add square x y ------------From Prelude---------------------- map f x (map f) x f x (n - 1) x f x n - 1 x f x (foldr1 f xs) f x foldr1 f xs showChar '[' . shows x . showl xs showChar '[] shows x showl xs
You just need to read from right to left accumulating a stack of arguments. When you hit a function that can consume some arguments, it does so. There is an error if you end up with more than one value on the argument stack.
Note that in your proposal, add square x y is parsed as add (square x) y instead of add (square (x y)), so it's not right associative either. As you explained, the parse of an expression depends the types of the sub-expressions, which imo is BAD. Just consider type inference... -- Zhanyong