Re: [Haskell-beginners] Pattern matching over functions

On 10-Dec-2011 11:17 AM, Ken KAWAMOTO wrote:

On Thu, Dec 8, 2011 at 3:14 PM, Brent Yorgey wrote:

...

On Wed, Dec 07, 2011 at 06:10:01PM +0100, Giacomo Tesio wrote:

...

I would find already very useful a compiler that is able to understand id f = f, that (\x -> 3 + x) == (\y = 3 + y) == (+3) even if it isn't able to see that (+3) == (\x -> 2 + 1 + x). But then we would lose referential transparency. As I understand, this would be against lazy evaluation since it would request to evaluate expressions in lambda, but I don't see how this relates to referential transparency. Can you elaborate this a little bit?

I second the question. From what I understand referential transparency means that an expression can be replaced by its value with no change to program semantics, or equivalently that a function always produces the same result/behaviour given the same input. How does determining whether two (pure) functions are equivalent break referential transparency? cheers! Graham

Thanks, Ken

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners