複数の関数のメモ化はできるか ref: http://qiita.com/items/93e2110ddb80e1e6f2c1

coin.hs

{-# LANGUAGE TupleSections #-}

module Main where

import Data.Function.YaMemo (Memo, memo)
import Data.Map (Map)

main :: IO ()
main = undefined

data FunID = A | B | C | D | E deriving (Eq, Ord, Enum)

usCoin :: (Ord a, Num a, Num b) => ((FunID, a) -> b) -> ((FunID, a) -> b)
usCoin _ (_,n) | n < 0 = 0
usCoin _ (A,_)         = 1
usCoin f (B,n)         = f (A,n) + f (B,n-5)
usCoin f (C,n)         = f (B,n) + f (C,n-10)
usCoin f (D,n)         = f (C,n) + f (D,n-25)
usCoin f (E,n)         = f (D,n) + f (E,n-50)

memoTable :: (Memo Map) (FunID, Integer) Integer
memoTable = undefined

usCoinMemo :: Integer -> Integer
usCoinMemo = (memo memoTable usCoin) . (E,)

file0.txt

usCoinA,usCoinB,usCoinC,usCoinD,usCoinE :: Integer -> Integer
usCoinA n | n < 0 = 0
usCoinA _         = 1
usCoinB n | n < 0 = 0
usCoinB n         = usCoinA n + usCoinB (n-5)
usCoinC n | n < 0 = 0
usCoinC n         = usCoinB n + usCoinC (n-10)
usCoinD n | n < 0 = 0
usCoinD n         = usCoinC n + usCoinD (n-25)
usCoinE n | n < 0 = 0
usCoinE n         = usCoinD n + usCoinE (n-50)

file1.txt

data FunID = A | B | C | D | E deriving (Eq,Ord,Enum)

usCoin :: FunID -> Integer -> Integer
usCoin _ n | n < 0 = 0
usCoin A _         = 1
usCoin B n         = usCoin A n + usCoin B (n-5)
usCoin C n         = usCoin B n + usCoin C (n-10)
usCoin D n         = usCoin C n + usCoin D (n-25)
usCoin E n         = usCoin D n + usCoin E (n-50)

file2.txt

usCoin :: (FunID, Integer) -> Integer
usCoin (_,n) | n < 0 = 0
usCoin (A,_)         = 1
usCoin (B,n)         = usCoin (A,n) + usCoin (B,n-5)
usCoin (C,n)         = usCoin (B,n) + usCoin (C,n-10)
usCoin (D,n)         = usCoin (C,n) + usCoin (D,n-25)
usCoin (E,n)         = usCoin (D,n) + usCoin (E,n-50)

file3.txt

usCoin _ (_,n) | n < 0 = 0
usCoin _ (A,_)         = 1
usCoin f (B,n)         = f (A,n) + f (B,n-5)
usCoin f (C,n)         = f (B,n) + f (C,n-10)
usCoin f (D,n)         = f (C,n) + f (D,n-25)
usCoin f (E,n)         = f (D,n) + f (E,n-50)