On 2011-02-15 21:12, John Meacham wrote:
Except for the fact that compilers don't actually implement call by need. An example would be the speculative evaluation of ghc. An interesting option. The things I've read say that it's not in the released ghc.
And local optimizations that affect asymptotic behavior are used all the time, to the point they are vital for a functioning compiler. The tail-call optimization turning O(n) space usage to O(1) being a prime example. Yes, that's essential.
I think that specifying call-by-need would be more confusing and contrary to what actually exists in the wild. Agreed that it may be confusing to call it "call-by-need" when there are several necessary exceptions. Apart from the name, I would hope it's possible to begin to tame this region of the Haskell spec.
-- Scott Turner