lerasimus/crafting-interpreters-hs
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

simplify scanner error type

Browse source
This commit is contained in:
Oleg Sobolev 2025-12-30 06:58:23 +03:00
parent ef7dc3603d
commit 8eeb671692
2 changed files with 8 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

4
app/Main.hs
View file

@ -8,7 +8,7 @@ run :: String -> IO ()
run source = do run source = do
let tokensMaybe = scanTokensFromSource source let tokensMaybe = scanTokensFromSource source
case tokensMaybe of case tokensMaybe of
Left UnexpectedCharacterError -> putStrLn "Unexpected character" Left (LexicalError s) -> putStrLn s
Right tokens -> do Right tokens -> do
let stmtMaybe = parse tokens let stmtMaybe = parse tokens
case stmtMaybe of case stmtMaybe of
@ -19,7 +19,7 @@ runEval :: String -> IO ()
runEval source = do runEval source = do
let tokensMaybe = scanTokensFromSource source let tokensMaybe = scanTokensFromSource source
object <- case tokensMaybe of object <- case tokensMaybe of
Left UnexpectedCharacterError -> putStrLn "Unexpected character" >> return NullObject Left (LexicalError s) -> putStrLn s >> return NullObject
Right tokens -> do Right tokens -> do
let exprMaybe = parseExpression tokens let exprMaybe = parseExpression tokens
case exprMaybe of case exprMaybe of

12
src/Lox/Scanner.hs
View file

@ -2,7 +2,7 @@ module Lox.Scanner (
TokenType (..), TokenType (..),
Object (..), Object (..),
Token (..), Token (..),
ScannerError (..), LexicalError (..),
scanTokensFromSource scanTokensFromSource
) where ) where
@ -45,16 +45,16 @@ data Token = Token {
data ScannerState = ScannerState {source :: String, current :: String, lineNumber :: Int} data ScannerState = ScannerState {source :: String, current :: String, lineNumber :: Int}
data ScannerError = UnexpectedCharacterError deriving Show data LexicalError = LexicalError String
emptyScannerState :: String -> ScannerState emptyScannerState :: String -> ScannerState
emptyScannerState source = emptyScannerState source =
ScannerState {source=source, current="", lineNumber=1} ScannerState {source=source, current="", lineNumber=1}
scanTokensFromSource :: String -> Either ScannerError [Token] scanTokensFromSource :: String -> Either LexicalError [Token]
scanTokensFromSource source = evalState scanTokens (emptyScannerState source) scanTokensFromSource source = evalState scanTokens (emptyScannerState source)
scanTokens :: State ScannerState (Either ScannerError [Token]) scanTokens :: State ScannerState (Either LexicalError [Token])
scanTokens = do scanTokens = do
atEnd <- isAtEnd atEnd <- isAtEnd
if atEnd then return . return <$> addToken EOF else do if atEnd then return . return <$> addToken EOF else do
@ -70,7 +70,7 @@ isAtEnd = gets scannerIsAtEnd
scannerIsAtEnd :: ScannerState -> Bool scannerIsAtEnd :: ScannerState -> Bool
scannerIsAtEnd ScannerState {source=source} = null source scannerIsAtEnd ScannerState {source=source} = null source
scanToken :: State ScannerState (Either ScannerError (Maybe Token)) scanToken :: State ScannerState (Either LexicalError (Maybe Token))
scanToken = do scanToken = do
resetCurrent resetCurrent
c <- advance c <- advance
@ -97,7 +97,7 @@ scanToken = do
'\r' -> return nothing '\r' -> return nothing
'\t' -> return nothing '\t' -> return nothing
'\n' -> modify (\s@(ScannerState {lineNumber=n}) -> s {lineNumber=n+1}) >> return nothing '\n' -> modify (\s@(ScannerState {lineNumber=n}) -> s {lineNumber=n+1}) >> return nothing
c -> if isDigit c then ok <$> scanNumber else if isAlpha c then ok <$> scanIdentifier else return $ Left UnexpectedCharacterError c -> if isDigit c then ok <$> scanNumber else if isAlpha c then ok <$> scanIdentifier else return $ Left $ LexicalError "Unexpected character"
scanString :: State ScannerState Token scanString :: State ScannerState Token
scanString = do scanString = do