Bags.hs

module Main where

import Test.Hspec

someNumbers2 :: [Int]
someNumbers2 = 1:2:3:[]

-- someNumbers3 = 4:5:[1,2,3]

mapList2 :: (Int -> Int) -> [Int] -> [Int]
mapList2 f [] = []
mapList2 f (h:t) = (f h):(mapList2 f t)

type Bag = [(Char, Int)]


listToBag :: [Char] -> Bag
listToBag l = foldr (bagInsert) [] l

bagInsert :: Char-> Bag -> Bag
bagInsert c ((a,i) : b)
 | c == a = (a, i + 1):b
 | otherwise = (a,i):(bagInsert c b)
bagInsert c [] = (c, 1):[]

bagEqual :: Bag -> Bag -> Bool
bagEqual b sb
 | b == sb = True
 | otherwise = False

main :: IO ()
main = hspec $ do
  describe "Bag" $ do
      describe "Adding" $ do
        it "Adds 'a' to empty Bag" $ do
          bagInsert 'a' emptybag `shouldBe` bagofa
        it "Adds 'b' to Bag of 'a'" $ do
          bagInsert 'b' bagofa `shouldBe` bagofba
        it "Adds 'a' to Bag of 'a'" $ do
          bagInsert 'a' bagofa `shouldBe` bagof2a

      describe "listTobag" $ do
        it "adds a list to a bag" $ do
          listToBag ['a','a','b'] `shouldBe` bagof2a1b

      describe "bagEqual" $ do
        it "true" $ do
          bagEqual bagofa bagofa `shouldBe` True
        it "false" $ do
          bagEqual bagofa bagof2a `shouldBe` False
        it "different order true" $ do
          bagEqual bagofab bagofba `shouldBe` True

  where
    emptybag = []::Bag
    bagofa = [('a',1)]::Bag
    bagof2a = [('a',2)]::Bag
    bagofab = [('b',1),('a',1)]::Bag
    bagofba = [('a',1),('b',1)]::Bag
    bagof2a1b = [('b',1),('a',2)]::Bag