Re: [Haskell-cafe] Functions are first class values in C

On Sat, 22 Dec 2007 17:25:34 +0200, Philippa Cowderoy wrote:

On Sat, 22 Dec 2007, Cristian Baboi wrote:

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On Sat, 22 Dec 2007 17:13:55 +0200, Philippa Cowderoy wrote:

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Here's a trivial example that does so:

(\x -> x) (\x -> x)

A lambda calculus classic that doesn't typecheck in Haskell:

(\x -> x x) (\x -> x x)

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Feel free to try evaluating it!

Thank you for your message.

I tryed and this is what I've got: ERROR - cannot find "show" function for: *** Expression : (\x -> x) (\x -> x) *** Of type : a -> a

Yep, that's because while it can evaluate it down to (\x -> x) your interpreter doesn't know how to print the result. You can demonstrate that it works by then passing in something to that result though:

((\x ->x) (\x -> x)) 1

I know that. The reason the interpreter doesn't know how to print the result is because converting functions to strings doesn't make sense. Thank you.

You'll have to evaluate the other one by hand. Don't spend too long with it though!

Don't worry, I'm lazy too :-)