Re: [Haskell-cafe] strange type mismatch when trying to use takusen

24 Nov 2006


      On 11/23/06, Seth Gordon  wrote:
...
takusen-test.hs:11:57:
     Couldn't match expected type `forall mark. DBM mark Session a'
            against inferred type `DBM mark sess ()'
     In the second argument of `($)', namely `main''
     In the expression:
           (withSession (connect [CAdbname "template1"])) $ main'
     In the expression:
         do (withSession (connect [CAdbname "template1"])) $ main'
Ah, the dreaded $ with existential types problem. $ is not quite
equivalent to application -- the type checker does something funny
with forall types. Just take out the $ and you'll be fine.

-- 
Taral 
"You can't prove anything."
    -- Gödel's Incompetence Theorem