Add Matrix.elem with a default

Author: JoelLefkowitz

src/Data/Matrix.purs

@@ -5,10 +5,10 @@ import Data.Sequences (max, pad)
 import Data.Coordinates (Coordinates, next)
 import Data.Array as Array
 import Control.Alternative (guard)
-import Data.Array (elem, filter, foldl, length, snoc, singleton, (..))
+import Data.Array (filter, foldl, length, snoc, singleton, (..))
 import Data.Array.NonEmpty (cons')
 import Data.String (joinWith)
-import Data.Maybe (Maybe, isJust)
+import Data.Maybe (Maybe, fromMaybe, isJust)
 
 newtype Matrix a
   = Matrix (Array (Array a))
@@ -34,6 +34,9 @@ index (Matrix rows) { x, y } = do
   row <- Array.index rows y
   Array.index row x
 
+elem :: ∀ a. Matrix a -> a -> Coordinates -> a
+elem m d x = fromMaybe d $ index m x
+
 contains :: ∀ a. Matrix a -> Coordinates -> Boolean
 contains m x = isJust $ index m x
 
@@ -45,7 +48,7 @@ points m = do
   pure { x, y }
 
 steps :: ∀ a. Matrix a -> Array Coordinates -> Array (Array Coordinates)
-steps m arr = snoc arr <$> (filter (\x -> contains m x && not elem x arr) $ next arr)
+steps m arr = snoc arr <$> (filter (\x -> contains m x && not Array.elem x arr) $ next arr)
 
 paths :: ∀ a. Matrix a -> Int -> Array (Array Coordinates)
 paths m n

src/Data/Word.purs

@@ -2,10 +2,9 @@ module Data.Word where
 
 import Prelude
 import Data.Coordinates (Coordinates)
-import Data.Matrix (Matrix, paths, index)
+import Data.Matrix (Matrix, paths, elem)
 import Data.Array ((..))
-import Data.String (joinWith)
-import Data.Maybe (fromMaybe)
+import Data.Foldable (fold)
 import Control.Alternative (guard)
 
 foreign import isWord :: String -> Boolean
@@ -19,7 +18,7 @@ boggle :: Matrix String -> Int -> Array Word
 boggle m n = do
   x <- 3 .. n
   path <- paths m x
-  guard <<< isWord $ join path
-  pure { path, word: join path }
-  where
-  join path = joinWith "" $ (\x -> fromMaybe "" $ index m x) <$> path
+  let
+    word = fold $ elem m "" <$> path
+  guard $ isWord word
+  pure { path, word }