September 2017 Update

Task/Rock-paper-scissors/Haskell/rock-paper-scissors.hs

@@ -1,36 +1,59 @@
-import System.Random
-
-data Choice = Rock | Paper | Scissors
- deriving (Show, Eq)
+import System.Random (randomRIO)
 
+data Choice
+  = Rock
+  | Paper
+  | Scissors
+  deriving (Show, Eq)
 
+beats :: Choice -> Choice -> Bool
 beats Paper Rock = True
 beats Scissors Paper = True
 beats Rock Scissors = True
 beats _ _ = False
 
-genrps (r,p,s) = fmap rps rand
-  where rps x | x <= s    = Rock
-              | x <= s+r  = Paper
-              | otherwise = Scissors
-        rand = randomRIO (1,r+p+s) :: IO Int
+genrps :: (Int, Int, Int) -> IO Choice
+genrps (r, p, s) = rps <$> rand
+  where
+    rps x
+      | x <= s = Rock
+      | x <= s + r = Paper
+      | otherwise = Scissors
+    rand = randomRIO (1, r + p + s) :: IO Int
 
-getrps = fmap rps getLine
-  where rps "scissors" = Scissors
-        rps "rock" = Rock
-        rps "paper" = Paper
-        rps _ = error "invalid input"
+getrps :: IO Choice
+getrps = rps <$> getLine
+  where
+    rps "scissors" = Scissors
+    rps "rock" = Rock
+    rps "paper" = Paper
+    rps _ = error "invalid input"
 
-game (r,p,s) = do putStrLn "rock, paper or scissors?"
-                  h <- getrps
-                  c <- genrps (r,p,s)
-                  putStrLn ("Player: " ++ show h ++ " Computer: " ++ show c)
-                  putStrLn (if beats h c then "player wins\n"
-                           else if beats c h then "player loses\n"
-                           else "draw\n")
-                  let rr = if h == Rock then r+1 else r
-                      pp = if h == Paper then p+1 else p
-                      ss = if h == Scissors then s+1 else s
-                  game (rr,pp,ss)
+game :: (Int, Int, Int) -> IO a
+game (r, p, s) = do
+  putStrLn "rock, paper or scissors?"
+  h <- getrps
+  c <- genrps (r, p, s)
+  putStrLn ("Player: " ++ show h ++ " Computer: " ++ show c)
+  putStrLn
+    (if beats h c
+       then "player wins\n"
+       else if beats c h
+              then "player loses\n"
+              else "draw\n")
+  let rr =
+        if h == Rock
+          then r + 1
+          else r
+      pp =
+        if h == Paper
+          then p + 1
+          else p
+      ss =
+        if h == Scissors
+          then s + 1
+          else s
+  game (rr, pp, ss)
 
-main = game (1,1,1)
+main :: IO a
+main = game (1, 1, 1)