From: Ramakrishnan Muthukrishnan Date: Sun, 21 Dec 2014 15:58:07 +0000 (+0530) Subject: hw5: exercise 5 X-Git-Url: https://git.rkrishnan.org/simplejson/components/com_hotproperty/css/configuration.rst?a=commitdiff_plain;h=8a179ee4342c0c1822038ef6a407c4c1464d24d3;p=yorgey.git hw5: exercise 5 --- diff --git a/hw5/Calc.hs b/hw5/Calc.hs index 3d8dd9b..edc0179 100644 --- a/hw5/Calc.hs +++ b/hw5/Calc.hs @@ -1,35 +1,40 @@ +{-# LANGUAGE TypeSynonymInstances #-} +{-# LANGUAGE FlexibleInstances #-} {-# OPTIONS_GHC -Wall #-} + module Calc where -import ExprT +import qualified ExprT as E import Parser +import StackVM + -eval :: ExprT -> Integer -- exercise 1 -eval (Lit n) = n -eval (Add e1 e2) = eval e1 + eval e2 -eval (Mul e1 e2) = eval e1 * eval e2 +eval :: E.ExprT -> Integer +eval (E.Lit n) = n +eval (E.Add e1 e2) = eval e1 + eval e2 +eval (E.Mul e1 e2) = eval e1 * eval e2 -- exercise 2 evalStr :: String -> Maybe Integer -- evalStr s = case (parseExp Lit Add Mul s) of -- Just e -> Just (eval e) -- Nothing -> Nothing -evalStr s = fmap eval (parseExp Lit Add Mul s) +evalStr s = fmap eval (parseExp E.Lit E.Add E.Mul s) class Expr a where lit :: Integer -> a add :: a -> a -> a mul :: a -> a -> a -instance Expr ExprT where - lit = Lit - add = Add - mul = Mul +instance Expr E.ExprT where + lit = E.Lit + add = E.Add + mul = E.Mul -reify :: ExprT -> ExprT +reify :: E.ExprT -> E.ExprT reify = id instance Expr Integer where @@ -56,3 +61,12 @@ instance Expr Mod7 where lit x = Mod7 (x `mod` 7) add (Mod7 x) (Mod7 y) = Mod7 ((x+y) `mod` 7) mul (Mod7 x) (Mod7 y) = Mod7 ((x*y) `mod` 7) + +-- exercise 5 +instance Expr Program where + lit x = [PushI x] + add x y = x ++ y ++ [Add] + mul x y = x ++ y ++ [Mul] + +compile :: String -> Maybe Program +compile = parseExp lit add mul