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
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.