2008/4/24 Wolfgang Jeltsch <[EMAIL PROTECTED]>: > Am Dienstag, 22. April 2008 01:58 schrieb John Meacham: > Why should the fixity of $ being changed? I thought, the reason for $ was > that you can write a $ b $ c.
Well, the reasons for this were discussed on another thread recently, but in brief, you can always rewrite "f $ g $ h $ x" as "f . g . h $ x", whereas there's no way to remove the parentheses from expressions like "f (g x) (h y) (k z)", which, if ($) were left associative like function application normally is, could be written "f $ g x $ h y $ k z". Moreover, using function composition in place of ($) where possible should probably be considered better style regardless, as expressions written that way effectively have more subexpressions, because (.) is an associative operator. For instance, in "f $ g $ h $ x", the substring "g $ h" is meaningless, but in "f . g . h $ x", we have that "g . h" is a well-typed function, as well as "f . g". Another good reason is that we certainly wouldn't want ($!) to have a different associativity than ($), and the left-associative form of ($!) is far more useful than the present right-associative one. Strictly applying a function to any parameter but the last currently requires awkward parentheses. In combination with left-associating ($), a left-associating ($!) will allow any combination of strict applications to be easily expressed. I tend to think of the present associativity of ($) as a kind of oversight which people started to abuse in place of proper function composition, whereas the alternate associativity has real benefits over this one. - Cale _______________________________________________ Haskell-prime mailing list Haskell-prime@haskell.org http://www.haskell.org/mailman/listinfo/haskell-prime
