-- Demonstrates State and Memoization monads on various examples
-- by Taylor Campbell, 3/2008

module Main where

import EditDistanceSM
import Fibonacci
import ParserST

main :: IO ()
main
    = do mainFib
         mainEdit
         mainParse

mainFib :: IO ()
mainFib
    = do putStr "Enter a natural number: "
         line <- getLine
         let n = read line
         putStrLn ("Fibonacci(" ++ show n ++ "): " ++ show (memoFib n))

mainEdit :: IO ()
mainEdit
    = do putStrLn "Enter two strings on separate lines:"
         a <- getLine
         b <- getLine
         putStrLn ("Edit distance: " ++ show (memoEditDistance a b))

mainParse :: IO ()
mainParse
    = do putStr "Enter a tree to parse: "
         input <- getLine
         putStrLn (maybe "Parse error!" show (parse testParser input))

data SimpleTree
    = Leaf
    | Branch SimpleTree SimpleTree
  deriving Show

testParser :: Parser SimpleTree
testParser = simpleTree

simpleTree :: Parser SimpleTree
simpleTree = simpleLeaf ! simpleBranch

simpleLeaf :: Parser SimpleTree
simpleLeaf = (char ? (== '*')) >-> (\ _ -> Leaf)

simpleBranch :: Parser SimpleTree
simpleBranch
    = ((char ? (== '(')) -# simpleTree # simpleTree #- (char ? (== ')')))
      >-> (\ (left, right) -> Branch left right)