Thomas, Stefan, Thanks for a most edifying exchange! i will reflect on this.
Best wishes, --greg On 6/28/07, Stefan Holdermans <[EMAIL PROTECTED]> wrote:
Thomas, > let x = ... in ... > > is only equal > > do x <- ...; ... > > in the Identity monad. Also, why would "do" be more primitive than > "let". That way you would have to use monads everywhere. Also, > let is treated specially by the type checker (IIRC) and there are > many, many other reasons not to do that. As you already hinted at in a later message, this has to do with let- bindings being potentially polymorphic and monadic bindings being necessarily monomorphic: import Control.Monad.Identity foo = let id = \x -> x in (id 'x', id 42) -- well-typed bar = runIdentity $ do id <- return (\x -> x) ; return (id 'x', id 42) -- ill-typed Cheers, Stefan
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