> It's available in Haskell as a first class citizen.
Not really. Haskell's laziness makes it easier to write functions that are memoized, but it does not automagically memoize functions. And how could it without incurring a non-trivial runtime space/time cost?
Haskell's purity is what makes it easier to write libraries that facilitate building memoized versions of functions in a transparent way (and that are obviously correct). For instance, I usually reach for [data-memocombinators][0], which happens to have a fibonacci example at the top of the docs:
import qualified Data.MemoCombinators as Memo
fib = Memo.integral fib'
where
fib' 0 = 0
fib' 1 = 1
fib' x = fib (x-1) + fib (x-2)
[0]: http://hackage.haskell.org/package/data-memocombinators-0.5.1/docs/Data-MemoCombinators.html
Not really. Haskell's laziness makes it easier to write functions that are memoized, but it does not automagically memoize functions. And how could it without incurring a non-trivial runtime space/time cost?
Haskell's purity is what makes it easier to write libraries that facilitate building memoized versions of functions in a transparent way (and that are obviously correct). For instance, I usually reach for [data-memocombinators][0], which happens to have a fibonacci example at the top of the docs: