| -----Original Message----- | From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Sam | Hughes | Sent: 16 September 2007 04:53 | To: Ryan Ingram | Cc: haskell-cafe | Subject: Re: [Haskell-cafe] How can I stop GHCi from calling "show" for IO actions? | | Ryan Ingram wrote: | > Prelude> let inf = repeat 1 | > Prelude> inf | > [1,1,(lots of output until I press ctrl-c),Interrupted. | > (I expect this to happen) | > Prelude> let x = inf | > (no output here!) | > Prelude> :t x | > x :: [Integer] | > Prelude> return inf | > [1,1,(lots of output until I press ctrl-c),Interrupted. | > (I also expect this to happen) | > Prelude> y <- return inf | > [1,1,(lots of output until I press ctrl-c),Interrupted. | > (I do not expect this to happen here!) | > Prelude> :t y | > | > <interactive>:1:0: Not in scope: 'y' | > | > Is this a bug? Why does "y <- return exp" have different behavior | > than "let y = exp"? Is there a way to make GHCi not print the result | > of an action but still make my variables get bound? | | That's weird. | | Prelude> (x,y) <- return $ (repeat 1, repeat 2) | Prelude> Just x <- return $ Just (repeat 1) | [1,1,1,... | Prelude> (x,_) <- return $ (repeat 1, repeat 2) | [1,1,1,... | Prelude> Just (x,y) <- return $ Just (repeat 1, repeat 2) | Prelude> | | It seems that GHCi outputs the contents of the variable you've created | when there's only one of them. Indeed, that is documented behaviour (first bullet here: http://www.haskell.org/ghc/docs/latest/html/users_guide/ch03s04.html#ghci-st... ) Perhaps it's confusing behaviour? If so do suggest an alternative. Simon