[hs] Clean up 2020_18

hs/src/Aoc/Y2020/D18.hs

@@ -14,44 +14,33 @@ import qualified Text.Megaparsec.Char.Lexer     as L
 import           Aoc.Day
 import           Aoc.Parse
 
-data Expr
-  = Lit Int
-  | Add Expr Expr
-  | Mul Expr Expr
-  deriving (Show)
-
-eval :: Expr -> Int
-eval (Lit l)   = l
-eval (Add a b) = eval a + eval b
-eval (Mul a b) = eval a * eval b
-
 lexeme :: Parser a -> Parser a
 lexeme = L.lexeme (void $ lineWhile isSpace)
 
 symbol :: T.Text -> Parser T.Text
 symbol = L.symbol (void $ lineWhile isSpace)
 
-parser :: [[Operator Parser Expr]] -> Parser [Expr]
+parser :: [[Operator Parser Int]] -> Parser [Int]
 parser table = manyLines expr
   where
     parens = between (symbol "(") (symbol ")")
-    term = (Lit <$> lexeme L.decimal) <|> parens expr
+    term = lexeme L.decimal <|> parens expr
     expr = makeExprParser term table
 
-table1 :: [[Operator Parser Expr]]
-table1 = [[InfixL (Add <$ symbol "+"), InfixL (Mul <$ symbol "*")]]
+table1 :: [[Operator Parser Int]]
+table1 = [[InfixL ((+) <$ symbol "+"), InfixL ((*) <$ symbol "*")]]
 
-table2 :: [[Operator Parser Expr]]
-table2 = [[InfixL (Add <$ symbol "+")], [InfixL (Mul <$ symbol "*")]]
+table2 :: [[Operator Parser Int]]
+table2 = [[InfixL ((+) <$ symbol "+")], [InfixL ((*) <$ symbol "*")]]
 
 solver :: FilePath -> T.Text -> IO ()
 solver path text = do
   putStrLn ">> Part 1"
-  parseAndSolve path text (parser table1) $ print . sum . map eval
+  parseAndSolve path text (parser table1) $ print . sum
 
   putStrLn ""
   putStrLn ">> Part 2"
-  parseAndSolve path text (parser table2) $ print . sum . map eval
+  parseAndSolve path text (parser table2) $ print . sum
 
 day :: Day
 day = dayText solver