feat: implement nextGuess with a more complex strategy

possible guesses are now consistent with previously received feedback

Proj2.hs

@@ -54,7 +54,7 @@ import Debug.Trace
 
 -- ==== DATA STRUCTURES =======================================================
 
--- TODO: INSERT COMMENT HERE
+-- contains possible guesses. a possible guess is consistent with all current -- and previous feedback given by the composer
 --
 type GameState = [[Pitch]]
 
@@ -155,10 +155,19 @@ initialGuess = (chord, chords)
   where
     chord : chords = allChords
 
--- TODO: implement me
+-- takes in the previous guess, the game state, and the feedback for the
+-- previous guess and outputs the next guess and a (reduced in size) game state
+--
+-- strategy:
+--  1. reduce the size of the search space by removing all guesses inconsistent
+--     with the answer received for the previous guess.
+--  2. TODO: mini-max?
 --
 nextGuess :: ([Pitch], GameState) -> (Int, Int, Int) -> ([Pitch], GameState)
-nextGuess (prevGuess, chord : chords) _ = (chord, chords)
+nextGuess (prevGuess, chords) answer = (guess, consistentChords)
+  where
+    guess : consistentChords = filter consistentWithAnswer chords
+    consistentWithAnswer chord = answer == feedback prevGuess chord
 
 -- ==== HELPER FUNCTIONS ======================================================