>>707
リスト使ったメモ化の理解にはいいんですけど、その例も実は遅いんですよね。!!がO(n)なので。
module Main where
import Data.Function
import qualified Data.Vector as V
main = do
let memo = fibMyMemo 50000
print $memo 50000
print $fibMemo 50000
fibMyMemo l = fib
where
fib = ((V.map f $ V.enumFromN 0 (l + 1)) V.!)
f 0 = 0 :: Integer
f 1 = 1
f n = fib (n -1) + fib (n -2)
memoize f = (map f [0 ..] !!)
fib f 0 = 0
fib f 1 = 1
fib f n = f (n - 1) + f (n - 2)
fibMemo = fix (memoize . fib)