[Haskell-cafe] Typing with co/contra-variance.

2008-04-03 Thread Ben Lippmeier
Hi all, I have some quick questions for the type theory people: If I write an expression: (if .. then 23 else Erk) In Haskell this would be an error, but perhaps I can assign it the type 'Top' (or 'Any') and then use reflection ala Data.Dynamic to inspect the type of this object at runtime

Re: [Haskell-cafe] Typing with co/contra-variance.

2008-04-03 Thread Luke Palmer
On Thu, Apr 3, 2008 at 9:58 AM, Ben Lippmeier [EMAIL PROTECTED] wrote: Hi all, I have some quick questions for the type theory people: If I write an expression: (if .. then 23 else Erk) In Haskell this would be an error, but perhaps I can assign it the type 'Top' (or 'Any') and then

Re: [Haskell-cafe] Typing with co/contra-variance.

2008-04-03 Thread Aaron Tomb
On Apr 3, 2008, at 10:41 AM, Luke Palmer wrote: On Thu, Apr 3, 2008 at 9:58 AM, Ben Lippmeier [EMAIL PROTECTED] wrote: Questions: 1) Could I perhaps wave my arms around and say something about the Int in the type of isEven being in a contra-variant position? Is this what is actually