Functional programming in Python

Zhanyong Wan
Fri, 25 May 2001 14:00:54 -0400

"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