Re: [Haskell-cafe] The difference between ($) and application

oleg@pobox.com wrote: [...]

However, if we try

...

t2' = W $ id

we get an error:

/tmp/t1.hs:13: Inferred type is less polymorphic than expected Quantified type variable `a' escapes Expected type: (a -> a) -> b Inferred type: (forall a1. a1 -> a1) -> W In the first argument of `($)', namely `W' In the definition of `t2'': t2' = W $ id

Incidentally, Hugs -98 gives a quite bizarre error message

ERROR "/tmp/t1.hs":13 - Use of W requires at least 1 argument

This is also the reason we write runST (do ...) instead of runST $ do ... isn't it?