Re: [Haskell-cafe] General function to count list elements?

And when the need gets big enough you pull out StablePtr and use that. :) On Sun, Apr 19, 2009 at 10:43 PM, Peter Verswyvelen wrote:

Sometimes I do miss the pragmatic C solution: - two function pointers that are equal surely represent the same functions (although in C nothing is really sure ;) - two function pointers that are different, might or might not represent that same functions. But this weak equality can sometimes be handy. For example, suppose you have a predicate a -> Bool, and a list of these predicates [a -> Bool], but you want to remove all functions that are obviously equal in the C way from the list for optimization... Okay big hack, and one could do this already with reallyUnsafePtrEquality# I guess... On Sat, Apr 18, 2009 at 6:02 PM, John A. De Goes wrote:

...

Two functions are equal iff they have the same domain and range and the same outputs for the same inputs. Simple to state, but extremely difficult to implement in a useful way, and impossible to implement in a perfect way.

If you had a compiler or algorithm capable of determining function equality, you could use it to prove or disprove arbitrary theorems in mathematics.

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