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7shi/Main.hs

Last active Aug 29, 2015
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module Main where
import Test.HUnit
import System.IO
data Expr = N Int
| Add [Expr]
| Mul [Expr]
deriving Show
eval (N x ) = x
eval (Add xs) = sum [eval x | x <- xs]
eval (Mul xs) = product [eval x | x <- xs]
isneg (N n) | n < 0 = True
isneg _ = False
str (N x) = show x
str (Add []) = ""
str (Add [x]) = str x
str (Add (x:y:zs))
| isneg y = str x ++ str (Add (y:zs))
str (Add (x:xs)) = str x ++ "+" ++ str (Add xs)
str (Mul []) = ""
str (Mul [x]) = str x
str (Mul (x:xs)) = str x ++ "*" ++ str (Mul xs)
tests = TestList
[ "eval 1" ~: eval (Add[N 1,N 1 ]) ~?= 1+1
, "eval 2" ~: eval (Add[N 2,N 3 ]) ~?= 2+3
, "eval 3" ~: eval (Add[N 5,N(-3)]) ~?= 5-3
, "eval 4" ~: eval (Mul[N 3,N 4 ]) ~?= 3*4
, "eval 5" ~: eval (Add[N 1,Mul[N 2,N 3]]) ~?= 1+2*3
, "eval 6" ~: eval (Mul[Add[N 1,N 2],N 3]) ~?= (1+2)*3
, "str 1" ~: str (Add[N 1,N 2 ,N 3 ]) ~?= "1+2+3"
, "str 2" ~: str (Add[N 1,N(-2),N(-3)]) ~?= "1-2-3"
, "str 3" ~: str (Mul[N 1,N 2 ,N 3 ]) ~?= "1*2*3"
, "str 4" ~: str (Add[N 1,Mul[N 2,N 3]]) ~?= "1+2*3"
]
main = do
runTestText (putTextToHandle stderr False) tests
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