Re: [Haskell-beginners] print []

That I understand. My question is that I have to enforce the type that specific way (don't want to use ExtendedDefaultRules) or is there some more generic way? On Wed, Aug 14, 2013 at 12:08 PM, David Virebayre < dav.vire+haskell@gmail.com> wrote:

2013/8/13 Lukas Lehner :

...

Good to know extension. And without it?

Someone correct me if I'm wrong, here's how I understand it:

To execute print [], ghc has to find which instance of Show to call. How could it find an instance without knowing the type ? [] could be a list of anything, and while in theory we know that in all cases it should print "[]", in practice ghc can't call that code if it doesn't know the type of the list.

David.

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