[Haskell-cafe] Re: Do expression definition

On 09/13/2010 12:23 PM, Michael Lazarev wrote:

2010/9/13 Henning Thielemann:

...

It means that variables bound by let, may be instantiated to different types later.

Can you give an example, please?

testOk = let f = id in (f 42, f True) --testNotOk :: Monad m => m (Int, Bool) --testNotOk = do f <- return id -- return (f 42, f True) Try uncommenting the 'testNotOk' definition.