refactor: idiomatic best-practices

Main.hs

@@ -39,4 +39,7 @@ toChord = fromJust . mapM toPitch . words
 -- | Prompt for a target and use guessTest to try to guess it.
 main :: IO ()
 main = do
-  putStr $ show avgGuesses
+  putStr "Target chord (3 pitches separated by spaces): "
+  hFlush stdout
+  text <- getLine
+  guessTest $ toChord text

Proj2.hs

@@ -54,14 +54,13 @@ module Proj2
     GameState,
     initialGuess,
     nextGuess,
-    avgGuesses,
   )
 where
 
-import Data.Function (on)
+import Data.Function
 import Data.List
 import Data.Map qualified as Map
-import Data.Ord (comparing)
+import Data.Ord
 import Data.Set qualified as Set
 
 -- ==== DATA STRUCTURES =======================================================
@@ -108,10 +107,9 @@ instance Show Octave where
 toPitch :: String -> Maybe Pitch
 toPitch [note, octave] = Pitch <$> charToNote note <*> charToOctave octave
   where
-    charToNote :: Char -> Maybe Note
+    charToNote =
-    charToNote c =
+      flip
         lookup
-        c
         [ ('A', A),
           ('B', B),
           ('C', C),
@@ -120,10 +118,9 @@ toPitch [note, octave] = Pitch <$> charToNote note <*> charToOctave octave
           ('F', F),
           ('G', G)
         ]
-    charToOctave :: Char -> Maybe Octave
+    charToOctave =
-    charToOctave c =
+      flip
         lookup
-        c
         [ ('1', One),
           ('2', Two),
           ('3', Three)
@@ -202,8 +199,8 @@ nextGuess (prevGuess, state) prevFeedback = (chosen, newState)
     chosen = fst $ minimumBy (comparing snd) scored
     newState = filter (/= chosen) candidates
 
-    scored = map (\x -> (x, score x candidates)) candidates
+    scored = map ((,) <*> (`score` candidates)) candidates
-    candidates = filter (\x -> prevFeedback == feedback prevGuess x) state
+    candidates = filter ((== prevFeedback) . feedback prevGuess) state
 
     -- average number of possible targets per candidate
     score candidate candidates = ((/) `on` fromIntegral) (sum l) (length l)
@@ -226,7 +223,7 @@ matches :: (Eq a, Show a) => [a] -> [a] -> Int
 matches xs ys = maximum permutationMatches
   where
     permutationMatches = map (pairwiseMatches xs) (permutations ys)
-    pairwiseMatches xs = length . filter (uncurry (==)) . zip xs
+    pairwiseMatches xs ys = length $ filter (uncurry (==)) $ zip xs ys
 
 -- outputs a list of all possible chords, where a chord is a list of unique
 -- pitches. this function happens to generate chords such that the pitches are
@@ -237,12 +234,11 @@ matches xs ys = maximum permutationMatches
 --
 allChords :: [[Pitch]]
 allChords =
-  [ chord
+  [ [p1, p2, p3]
     | p1 <- allPitches,
       p2 <- allPitches,
-      p3 <- allPitches,
-      let chord = [p1, p2, p3],
       p1 < p2,
+      p3 <- allPitches,
       p2 < p3
   ]
   where
@@ -251,22 +247,3 @@ allChords =
         | note <- [minBound .. maxBound],
           octave <- [minBound .. maxBound]
       ]
-
--- ==== TESTING ===============================================================
-
-guessTest :: [Pitch] -> Int
-guessTest target = loop target guess other 1
-  where
-    (guess, other) = initialGuess
-
-loop :: [Pitch] -> [Pitch] -> GameState -> Int -> Int
-loop target guess other guesses
-  | answer == (3, 0, 0) = guesses
-  | otherwise = loop target guess' other' (guesses + 1)
-  where
-    answer = feedback target guess
-    (guess', other') = nextGuess (guess, other) answer
-
-avgGuesses = fromIntegral (sum results) / fromIntegral (length results)
-  where
-    results = map guessTest allChords

README.md

@@ -1,12 +1,4 @@
 # Spec
-## Best first guess 
-### All different
-[C1, D2, E3]: 4.27
-[A1, D2, G3]: 4.25 
-### Same notes 
-[D1, D2, D3]: 4.80 
-### Same octaves 
-[C2, D2, E2]: 4.34 
 ## Tips to improve `nextGuess`
 The best results can be had by carefully choosing each guess so that it is most
 likely to leave a small remaining list of possible targets. You can do this by

justfile

@@ -12,4 +12,4 @@ build:
 
 # run musician 
 run:
-  time ./target/{{exec}}
+  ./target/{{exec}}