converted to Text

app/Main.hs

@@ -3,16 +3,17 @@ module Main where
 import Check
 import Expr
 import Parser
+import qualified Data.Text.IO as T
 import System.IO
 
 main :: IO ()
 main = do
-    _ <- putStr "> "
+    _ <- T.putStr "> "
     _ <- hFlush stdout
-    input <- getLine
+    input <- T.getLine
     case pAll input of
-        Left err -> putStrLn err
+        Left err -> T.putStrLn err
         Right expr -> case findType [] expr of
-            Right ty -> putStrLn $ pretty expr ++ " : " ++ pretty ty
+            Right ty -> T.putStrLn $ pretty expr <> " : " <> pretty ty
             Left err -> print err
     main

dependent-lambda.cabal

@@ -39,6 +39,8 @@ library dependent-lambda-lib
                       , parser-combinators
                       , mtl
     default-language:   Haskell2010
+    default-extensions: OverloadedStrings
+                      , GADTs
 
 common warnings
     ghc-options: -Wall
@@ -49,8 +51,11 @@ executable dependent-lambda
 
     build-depends:      base ^>=4.19.1.0
                       , dependent-lambda-lib
+                      , text
     hs-source-dirs:     app
     default-language:   Haskell2010
+    default-extensions: OverloadedStrings
+                      , GADTs
 
 test-suite tests
     type:               exitcode-stdio-1.0
@@ -60,6 +65,9 @@ test-suite tests
                       , CheckTests
     build-depends:      base ^>=4.19.1.0
                       , HUnit
+                      , text
                       , dependent-lambda-lib
     hs-source-dirs:     tests
     default-language:   Haskell2010
+    default-extensions: OverloadedStrings
+                      , GADTs

lib/Check.hs

@@ -2,20 +2,22 @@ module Check (TypeCheckError (..), CheckResult (..), findType) where
 
 import Control.Monad.Except (MonadError (throwError))
 import Data.List (intercalate, (!?))
+import Data.Text (Text)
+import qualified Data.Text as T
 
 import Control.Monad (unless)
 import Expr
 
 type Context = [Expr]
 
-data TypeCheckError = SquareUntyped | UnboundVariable String | NotASort Expr Expr | ExpectedPiType Expr Expr | NotEquivalent Expr Expr Expr
+data TypeCheckError = SquareUntyped | UnboundVariable Text | NotASort Expr Expr | ExpectedPiType Expr Expr | NotEquivalent Expr Expr Expr deriving (Eq)
 
 instance Show TypeCheckError where
     show SquareUntyped = "□ does not have a type"
-    show (UnboundVariable x) = "Unbound variable: " ++ x
+    show (UnboundVariable x) = "Unbound variable: " ++ T.unpack x
-    show (NotASort x t) = "Expected " ++ pretty x ++ " to have type * or □, instead found " ++ pretty t
+    show (NotASort x t) = "Expected " ++ prettyS x ++ " to have type * or □, instead found " ++ prettyS t
-    show (ExpectedPiType m a) = pretty m ++ " : " ++ pretty a ++ " is not a function"
+    show (ExpectedPiType m a) = prettyS m ++ " : " ++ prettyS a ++ " is not a function"
-    show (NotEquivalent a a' e) = "Cannot unify " ++ pretty a ++ " with " ++ pretty a' ++ " when evaluating " ++ pretty e
+    show (NotEquivalent a a' e) = "Cannot unify " ++ prettyS a ++ " with " ++ prettyS a' ++ " when evaluating " ++ prettyS e
 
 type CheckResult = Either TypeCheckError
 

lib/Expr.hs

@@ -1,16 +1,16 @@
-{-# LANGUAGE GADTs #-}
-
 module Expr where
 
 import Data.Function (on)
+import Data.Text (Text)
+import qualified Data.Text as T
 
 data Expr where
-    Var :: Integer -> String -> Expr
+    Var :: Integer -> Text -> Expr
     Star :: Expr
     Square :: Expr
     App :: Expr -> Expr -> Expr
-    Abs :: String -> Expr -> Expr -> Expr
+    Abs :: Text -> Expr -> Expr -> Expr
-    Pi :: String -> Expr -> Expr -> Expr
+    Pi :: Text -> Expr -> Expr -> Expr
     deriving (Show)
 
 instance Eq Expr where
@@ -32,58 +32,61 @@ occursFree n (Pi _ a b) = occursFree n a || occursFree (n + 1) b
 
 {- --------------------- PRETTY PRINTING ----------------------------- -}
 
-parenthesize :: String -> String
+parenthesize :: Text -> Text
-parenthesize s = "(" ++ s ++ ")"
+parenthesize s = T.concat ["(", s, ")"]
 
-collectLambdas :: Expr -> ([(String, Expr)], Expr)
+collectLambdas :: Expr -> ([(Text, Expr)], Expr)
 collectLambdas (Abs x ty body) = ((x, ty) : params, final)
   where
     (params, final) = collectLambdas body
 collectLambdas e = ([], e)
 
-collectPis :: Expr -> ([(String, Expr)], Expr)
+collectPis :: Expr -> ([(Text, Expr)], Expr)
 collectPis p@(Pi "" _ _) = ([], p)
 collectPis (Pi x ty body) = ((x, ty) : params, final)
   where
     (params, final) = collectPis body
 collectPis e = ([], e)
 
-groupParams :: [(String, Expr)] -> [([String], Expr)]
+groupParams :: [(Text, Expr)] -> [([Text], Expr)]
 groupParams = foldr addParam []
   where
-    addParam :: (String, Expr) -> [([String], Expr)] -> [([String], Expr)]
+    addParam :: (Text, Expr) -> [([Text], Expr)] -> [([Text], Expr)]
     addParam (x, t) [] = [([x], t)]
     addParam (x, t) l@((xs, s) : rest)
         | incIndices t == s = (x : xs, t) : rest
         | otherwise = ([x], t) : l
 
-showParamGroup :: ([String], Expr) -> String
+showParamGroup :: ([Text], Expr) -> Text
-showParamGroup (ids, ty) = parenthesize $ unwords ids ++ " : " ++ pretty ty
+showParamGroup (ids, ty) = parenthesize $ T.unwords ids <> " : " <> pretty ty
 
-helper :: Integer -> Expr -> String
+helper :: Integer -> Expr -> Text
 helper _ (Var _ s) = s
 helper _ Star = "*"
 helper _ Square = "□"
 helper k (App e1 e2) = if k > 3 then parenthesize res else res
   where
-    res = helper 3 e1 ++ " " ++ helper 4 e2
+    res = helper 3 e1 <> " " <> helper 4 e2
 helper k (Pi "" t1 t2) = if k > 2 then parenthesize res else res
   where
-    res = helper 3 t1 ++ " -> " ++ helper 2 t2
+    res = helper 3 t1 <> " -> " <> helper 2 t2
 helper k e@(Pi{}) = if k > 2 then parenthesize res else res
   where
     (params, body) = collectPis e
     grouped = showParamGroup <$> groupParams params
-    res = "∏ " ++ unwords grouped ++ " . " ++ pretty body
+    res = "∏ " <> T.unwords grouped <> " . " <> pretty body
 helper k e@(Abs{}) = if k >= 1 then parenthesize res else res
   where
     (params, body) = collectLambdas e
     grouped = showParamGroup <$> groupParams params
-    res = "λ " ++ unwords grouped ++ " . " ++ pretty body
+    res = "λ " <> T.unwords grouped <> " . " <> pretty body
 
-pretty :: Expr -> String
+pretty :: Expr -> Text
 pretty = helper 0
 
+prettyS :: Expr -> String
+prettyS = T.unpack . pretty
+
 {- --------------- ACTUAL MATH STUFF ---------------- -}
 
 isSort :: Expr -> Bool

lib/Parser.hs

@@ -7,20 +7,22 @@ import Data.Functor.Identity
 import Data.List (elemIndex)
 import Data.List.NonEmpty (NonEmpty ((:|)))
 import qualified Data.List.NonEmpty as NE
+import Data.Text (Text)
+import qualified Data.Text as T
 import Expr (Expr (..), incIndices)
 import Text.Megaparsec hiding (State)
 import Text.Megaparsec.Char
 import qualified Text.Megaparsec.Char.Lexer as L
 
-type InnerState = [String]
+type InnerState = [Text]
 
-data CustomErrors = UnboundVariable String [String] deriving (Eq, Ord, Show)
+data CustomErrors = UnboundVariable Text [Text] deriving (Eq, Ord, Show)
 
 instance ShowErrorComponent CustomErrors where
     showErrorComponent (UnboundVariable var bound) =
-        "Unbound variable: " ++ var ++ ". Did you mean one of: " ++ unwords bound ++ "?"
+        "Unbound variable: " ++ T.unpack var ++ ". Did you mean one of: " ++ T.unpack (T.unwords bound) ++ "?"
 
-type Parser = ParsecT CustomErrors String (State InnerState)
+type Parser = ParsecT CustomErrors Text (State InnerState)
 
 skipSpace :: Parser ()
 skipSpace =
@@ -32,11 +34,11 @@ skipSpace =
 lexeme :: Parser a -> Parser a
 lexeme = L.lexeme skipSpace
 
-pIdentifier :: Parser String
+pIdentifier :: Parser Text
 pIdentifier = label "identifier" $ lexeme $ do
     firstChar <- letterChar <|> char '_'
     rest <- many $ alphaNumChar <|> char '_'
-    return $ firstChar : rest
+    return $ T.pack (firstChar : rest) -- Still need T.pack here as we're building from chars
 
 pVar :: Parser Expr
 pVar = label "variable" $ lexeme $ do
@@ -46,12 +48,10 @@ pVar = label "variable" $ lexeme $ do
         Just i -> return $ Var (fromIntegral i) var
         Nothing -> customFailure $ UnboundVariable var binders
 
-defChoice :: NE.NonEmpty String -> Parser ()
+defChoice :: NE.NonEmpty Text -> Parser ()
-defChoice options = lexeme $ label labelText $ void $ choice $ NE.map string options
+defChoice options = lexeme $ label (T.unpack $ NE.head options) $ void $ choice $ NE.map chunk options
-  where
-    labelText = NE.head options
 
-pParamGroup :: Parser [(String, Expr)]
+pParamGroup :: Parser [(Text, Expr)]
 pParamGroup = lexeme $ label "parameter group" $ between (char '(') (char ')') $ do
     idents <- some pIdentifier
     _ <- defChoice $ ":" :| []
@@ -59,7 +59,7 @@ pParamGroup = lexeme $ label "parameter group" $ between (char '(') (char ')') $
     modify (flip (foldl $ flip (:)) idents)
     pure $ zip idents (iterate incIndices ty)
 
-pParams :: Parser [(String, Expr)]
+pParams :: Parser [(Text, Expr)]
 pParams = concat <$> some pParamGroup
 
 pLAbs :: Parser Expr
@@ -112,5 +112,5 @@ pAppTerm = lexeme $ pLAbs <|> pPAbs <|> pApp
 pExpr :: Parser Expr
 pExpr = lexeme $ try pArrow <|> pAppTerm
 
-pAll :: String -> Either String Expr
+pAll :: Text -> Either Text Expr
-pAll input = first errorBundlePretty $ fst $ runIdentity $ runStateT (runParserT pExpr "" input) []
+pAll input = first (T.pack . errorBundlePretty) $ fst $ runIdentity $ runStateT (runParserT pExpr "" input) []

tests/ParserTests.hs

@@ -1,5 +1,7 @@
 module ParserTests (tests) where
 
+import Data.Text (Text)
+import qualified Data.Text as T
 import Expr (Expr (..))
 import Parser (pAll)
 import Test.HUnit