James Eversole
f9864b8361
Adds support for REPL namespacing, primarily to avoid `main` collisions. Also adds a library function for an ergonomic pattern matching function that I've been noodling on. I might explore ways to make list syntax less annoying specifically for pattern matching like this.
313 lines
8.9 KiB
Haskell
313 lines
8.9 KiB
Haskell
module Parser where
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import Lexer
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import Research
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import Control.Monad (void)
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import Control.Monad.State
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import Data.List.NonEmpty (toList)
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import Data.Void (Void)
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import Text.Megaparsec
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import Text.Megaparsec.Error (ParseErrorBundle, errorBundlePretty)
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import qualified Data.Set as Set
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data PState = PState
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{ parenDepth :: Int
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, bracketDepth :: Int
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} deriving (Show)
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type ParserM = StateT PState (Parsec Void [LToken])
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satisfyM :: (LToken -> Bool) -> ParserM LToken
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satisfyM f = do
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token <- lift (satisfy f)
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modify' (updateDepth token)
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return token
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updateDepth :: LToken -> PState -> PState
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updateDepth LOpenParen st = st { parenDepth = parenDepth st + 1 }
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updateDepth LOpenBracket st = st { bracketDepth = bracketDepth st + 1 }
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updateDepth LCloseParen st = st { parenDepth = parenDepth st - 1 }
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updateDepth LCloseBracket st = st { bracketDepth = bracketDepth st - 1 }
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updateDepth _ st = st
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topLevelNewline :: ParserM ()
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topLevelNewline = do
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st <- get
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if parenDepth st == 0 && bracketDepth st == 0
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then void (satisfyM (== LNewline))
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else fail "Top-level exit in nested context (paren or bracket)"
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parseProgram :: [LToken] -> Either (ParseErrorBundle [LToken] Void) [TricuAST]
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parseProgram tokens =
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runParser (evalStateT (parseProgramM <* finalizeDepth <* eof) (PState 0 0)) "" tokens
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parseSingleExpr :: [LToken] -> Either (ParseErrorBundle [LToken] Void) TricuAST
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parseSingleExpr tokens =
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runParser (evalStateT (scnParserM *> parseExpressionM <* finalizeDepth <* eof) (PState 0 0)) "" tokens
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finalizeDepth :: ParserM ()
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finalizeDepth = do
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st <- get
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case (parenDepth st, bracketDepth st) of
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(0, 0) -> pure ()
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(p, b) -> fail $ "Unmatched tokens: " ++ show (p, b)
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parseTricu :: String -> [TricuAST]
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parseTricu input =
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case lexTricu input of
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[] -> []
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toks ->
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case parseProgram toks of
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Left err -> errorWithoutStackTrace (handleParseError err)
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Right asts -> asts
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parseSingle :: String -> TricuAST
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parseSingle input =
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case lexTricu input of
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[] -> SEmpty
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toks ->
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case parseSingleExpr toks of
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Left err -> errorWithoutStackTrace (handleParseError err)
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Right ast -> ast
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parseProgramM :: ParserM [TricuAST]
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parseProgramM = do
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skipMany topLevelNewline
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importNodes <- many (do
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node <- parseImportM
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skipMany topLevelNewline
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return node)
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skipMany topLevelNewline
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exprs <- sepEndBy parseOneExpression (some topLevelNewline)
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skipMany topLevelNewline
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return (importNodes ++ exprs)
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parseImportM :: ParserM TricuAST
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parseImportM = do
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LImport filePath moduleName <- satisfyM isImport
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pure (SImport filePath moduleName)
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where
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isImport (LImport _ _) = True
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isImport _ = False
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parseOneExpression :: ParserM TricuAST
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parseOneExpression = scnParserM *> parseExpressionM
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scnParserM :: ParserM ()
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scnParserM = skipMany $ do
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t <- lookAhead anySingle
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st <- get
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if | (parenDepth st > 0 || bracketDepth st > 0) && (t == LNewline) ->
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void $ satisfyM (== LNewline)
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| otherwise ->
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fail "In nested context or no space token" <|> empty
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eofM :: ParserM ()
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eofM = lift eof
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parseExpressionM :: ParserM TricuAST
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parseExpressionM = choice
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[ try parseFunctionM
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, try parseLambdaM
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, try parseLambdaExpressionM
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, try parseListLiteralM
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, try parseApplicationM
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, try parseTreeTermM
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, parseLiteralM
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]
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parseFunctionM :: ParserM TricuAST
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parseFunctionM = do
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let ident = (\case LIdentifier _ -> True; _ -> False)
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LIdentifier name <- satisfyM ident
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args <- many $ satisfyM ident
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_ <- satisfyM (== LAssign)
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scnParserM
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body <- parseExpressionM
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pure (SDef name (map getIdentifier args) body)
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parseLambdaM :: ParserM TricuAST
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parseLambdaM = do
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let ident = (\case LIdentifier _ -> True; _ -> False)
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_ <- satisfyM (== LBackslash)
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params <- some (satisfyM ident)
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_ <- satisfyM (== LColon)
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scnParserM
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body <- parseLambdaExpressionM
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pure $ foldr (\param acc -> SLambda [getIdentifier param] acc) body params
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parseLambdaExpressionM :: ParserM TricuAST
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parseLambdaExpressionM = choice
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[ try parseLambdaApplicationM
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, parseAtomicLambdaM
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]
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parseAtomicLambdaM :: ParserM TricuAST
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parseAtomicLambdaM = choice
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[ parseVarM
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, parseTreeLeafM
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, parseLiteralM
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, parseListLiteralM
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, try parseLambdaM
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, between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) parseLambdaExpressionM
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]
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parseApplicationM :: ParserM TricuAST
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parseApplicationM = do
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func <- parseAtomicBaseM
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scnParserM
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args <- many $ do
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scnParserM
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arg <- parseAtomicM
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return arg
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return $ foldl SApp func args
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parseLambdaApplicationM :: ParserM TricuAST
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parseLambdaApplicationM = do
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func <- parseAtomicLambdaM
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scnParserM
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args <- many $ do
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arg <- parseAtomicLambdaM
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scnParserM
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pure arg
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pure $ foldl SApp func args
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parseAtomicBaseM :: ParserM TricuAST
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parseAtomicBaseM = choice
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[ parseTreeLeafM
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, parseGroupedM
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]
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parseTreeLeafM :: ParserM TricuAST
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parseTreeLeafM = do
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let keyword = (\case LKeywordT -> True; _ -> False)
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_ <- satisfyM keyword
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notFollowedBy $ lift $ satisfy (== LAssign)
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pure TLeaf
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parseTreeTermM :: ParserM TricuAST
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parseTreeTermM = do
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base <- parseTreeLeafOrParenthesizedM
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rest <- many parseTreeLeafOrParenthesizedM
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pure (foldl combine base rest)
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where
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combine acc next
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| TLeaf <- acc = TStem next
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| TStem t <- acc = TFork t next
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| TFork _ _ <- acc = TFork acc next
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parseTreeLeafOrParenthesizedM :: ParserM TricuAST
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parseTreeLeafOrParenthesizedM = choice
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[ between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) parseTreeTermM
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, parseTreeLeafM
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]
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parseAtomicM :: ParserM TricuAST
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parseAtomicM = choice
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[ parseVarM
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, parseTreeLeafM
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, parseListLiteralM
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, parseGroupedM
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, parseLiteralM
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]
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parseGroupedM :: ParserM TricuAST
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parseGroupedM = between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) $
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scnParserM *> parseExpressionM <* scnParserM
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parseLiteralM :: ParserM TricuAST
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parseLiteralM = choice
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[ parseIntLiteralM
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, parseStrLiteralM
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]
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parseListLiteralM :: ParserM TricuAST
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parseListLiteralM = do
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_ <- satisfyM (== LOpenBracket)
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elements <- many $ do
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scnParserM
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parseListItemM
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scnParserM
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_ <- satisfyM (== LCloseBracket)
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pure (SList elements)
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parseListItemM :: ParserM TricuAST
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parseListItemM = choice
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[ parseGroupedItemM
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, parseListLiteralM
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, parseSingleItemM
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]
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parseGroupedItemM :: ParserM TricuAST
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parseGroupedItemM = do
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_ <- satisfyM (== LOpenParen)
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inner <- parseExpressionM
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_ <- satisfyM (== LCloseParen)
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pure inner
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parseSingleItemM :: ParserM TricuAST
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parseSingleItemM = do
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token <- satisfyM (\case LIdentifier _ -> True; LKeywordT -> True; _ -> False)
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if | LIdentifier name <- token -> pure (SVar name)
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| token == LKeywordT -> pure TLeaf
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| otherwise -> fail "Unexpected token in list item"
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parseVarM :: ParserM TricuAST
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parseVarM = do
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token <- satisfyM (\case
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LNamespace _ -> True
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LIdentifier _ -> True
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_ -> False)
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case token of
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LNamespace ns -> do
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_ <- satisfyM (== LDot)
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LIdentifier name <- satisfyM (\case LIdentifier _ -> True; _ -> False)
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pure $ SVar (ns ++ "." ++ name)
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LIdentifier name
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| name == "t" || name == "!result" ->
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fail ("Reserved keyword: " ++ name ++ " cannot be assigned.")
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| otherwise -> pure (SVar name)
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_ -> fail "Unexpected token while parsing variable"
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parseIntLiteralM :: ParserM TricuAST
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parseIntLiteralM = do
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let intL = (\case LIntegerLiteral _ -> True; _ -> False)
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token <- satisfyM intL
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if | LIntegerLiteral value <- token ->
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pure (SInt value)
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| otherwise ->
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fail "Unexpected token while parsing integer literal"
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parseStrLiteralM :: ParserM TricuAST
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parseStrLiteralM = do
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let strL = (\case LStringLiteral _ -> True; _ -> False)
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token <- satisfyM strL
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if | LStringLiteral value <- token ->
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pure (SStr value)
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| otherwise ->
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fail "Unexpected token while parsing string literal"
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getIdentifier :: LToken -> String
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getIdentifier (LIdentifier name) = name
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getIdentifier _ = errorWithoutStackTrace "Expected identifier"
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handleParseError :: ParseErrorBundle [LToken] Void -> String
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handleParseError bundle =
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let errors = bundleErrors bundle
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formattedErrors = map formatError (Data.List.NonEmpty.toList errors)
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in unlines ("Parse error(s) encountered:" : formattedErrors)
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formatError :: ParseError [LToken] Void -> String
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formatError (TrivialError offset unexpected expected) =
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let unexpectedMsg = case unexpected of
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Just x -> "unexpected token " ++ show x
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Nothing -> "unexpected end of input"
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expectedMsg = if null expected
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then ""
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else "expected " ++ show (Set.toList expected)
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in "Parse error at offset " ++ show offset ++ ": " ++ unexpectedMsg ++
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if null expectedMsg then "" else " " ++ expectedMsg
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formatError (FancyError offset _) =
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"Parse error at offset " ++ show offset ++ ": unexpected FancyError"
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