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|
-----------------------------------------------------------------------------
The lexer.
(c) 1993-2001 Andy Gill, Simon Marlow
-----------------------------------------------------------------------------
> module Lexer (
> Token(..),
> TokenId(..),
> lexer ) where
> import ParseMonad
> import Data.Char ( isSpace, isAlphaNum, isDigit, digitToInt )
> data Token
> = TokenInfo String TokenId
> | TokenNum Int TokenId
> | TokenKW TokenId
> | TokenEOF
> tokenToId :: Token -> TokenId
> tokenToId (TokenInfo _ i) = i
> tokenToId (TokenNum _ i) = i
> tokenToId (TokenKW i) = i
> tokenToId TokenEOF = error "tokenToId TokenEOF"
> instance Eq Token where
> i == i' = tokenToId i == tokenToId i'
> instance Ord Token where
> i <= i' = tokenToId i <= tokenToId i'
> data TokenId
> = TokId -- words and symbols
> | TokSpecId_TokenType -- %tokentype
> | TokSpecId_Token -- %token
> | TokSpecId_Name -- %name
> | TokSpecId_Partial -- %partial
> | TokSpecId_Lexer -- %lexer
> | TokSpecId_ImportedIdentity -- %importedidentity
> | TokSpecId_Monad -- %monad
> | TokSpecId_Nonassoc -- %nonassoc
> | TokSpecId_Left -- %left
> | TokSpecId_Right -- %right
> | TokSpecId_Prec -- %prec
> | TokSpecId_Expect -- %expect
> | TokSpecId_Error -- %error
> | TokSpecId_Attributetype -- %attributetype
> | TokSpecId_Attribute -- %attribute
> | TokCodeQuote -- stuff inside { .. }
> | TokColon -- :
> | TokSemiColon -- ;
> | TokDoubleColon -- ::
> | TokDoublePercent -- %%
> | TokBar -- |
> | TokNum -- Integer
> | TokParenL -- (
> | TokParenR -- )
> | TokComma -- ,
> deriving (Eq,Ord
#ifdef DEBUG
> ,Show
#endif
> )
ToDo: proper text instance here, for use in parser error messages.
> lexer :: (Token -> P a) -> P a
> lexer cont = P lexer'
> where lexer' "" = returnToken cont TokenEOF ""
> lexer' ('-':'-':r) = lexer' (dropWhile (/= '\n') r)
> lexer' ('{':'-':r) = \line -> lexNestedComment line lexer' r line
> lexer' (c:rest) = nextLex cont c rest
> returnToken :: (t -> P a) -> t -> String -> Int -> ParseResult a
> returnToken cont tok = runP (cont tok)
> nextLex :: (Token -> P a) -> Char -> String -> Int -> ParseResult a
> nextLex cont c = case c of
> '\n' -> \rest line -> returnToken lexer cont rest (line+1)
> '%' -> lexPercent cont
> ':' -> lexColon cont
> ';' -> returnToken cont (TokenKW TokSemiColon)
> '|' -> returnToken cont (TokenKW TokBar)
> '\'' -> lexChar cont
> '"'{-"-}-> lexString cont
> '{' -> lexCode cont
> '(' -> returnToken cont (TokenKW TokParenL)
> ')' -> returnToken cont (TokenKW TokParenR)
> ',' -> returnToken cont (TokenKW TokComma)
> _
> | isSpace c -> runP (lexer cont)
> | c >= 'a' && c <= 'z'
> || c >= 'A' && c <= 'Z' -> lexId cont c
> | isDigit c -> lexNum cont c
> _ -> lexError ("lexical error before `" ++ c : "'")
Percents come in two forms, in pairs, or
followed by a special identifier.
> lexPercent :: (Token -> P a) -> [Char] -> Int -> ParseResult a
> lexPercent cont s = case s of
> '%':rest -> returnToken cont (TokenKW TokDoublePercent) rest
> 't':'o':'k':'e':'n':'t':'y':'p':'e':rest ->
> returnToken cont (TokenKW TokSpecId_TokenType) rest
> 't':'o':'k':'e':'n':rest ->
> returnToken cont (TokenKW TokSpecId_Token) rest
> 'n':'a':'m':'e':rest ->
> returnToken cont (TokenKW TokSpecId_Name) rest
> 'p':'a':'r':'t':'i':'a':'l':rest ->
> returnToken cont (TokenKW TokSpecId_Partial) rest
> 'i':'m':'p':'o':'r':'t':'e':'d':'i':'d':'e':'n':'t':'i':'t':'y':rest ->
> returnToken cont (TokenKW TokSpecId_ImportedIdentity) rest
> 'm':'o':'n':'a':'d':rest ->
> returnToken cont (TokenKW TokSpecId_Monad) rest
> 'l':'e':'x':'e':'r':rest ->
> returnToken cont (TokenKW TokSpecId_Lexer) rest
> 'n':'o':'n':'a':'s':'s':'o':'c':rest ->
> returnToken cont (TokenKW TokSpecId_Nonassoc) rest
> 'l':'e':'f':'t':rest ->
> returnToken cont (TokenKW TokSpecId_Left) rest
> 'r':'i':'g':'h':'t':rest ->
> returnToken cont (TokenKW TokSpecId_Right) rest
> 'p':'r':'e':'c':rest ->
> returnToken cont (TokenKW TokSpecId_Prec) rest
> 'e':'x':'p':'e':'c':'t':rest ->
> returnToken cont (TokenKW TokSpecId_Expect) rest
> 'e':'r':'r':'o':'r':rest ->
> returnToken cont (TokenKW TokSpecId_Error) rest
> 'a':'t':'t':'r':'i':'b':'u':'t':'e':'t':'y':'p':'e':rest ->
> returnToken cont (TokenKW TokSpecId_Attributetype) rest
> 'a':'t':'t':'r':'i':'b':'u':'t':'e':rest ->
> returnToken cont (TokenKW TokSpecId_Attribute) rest
> _ -> lexError ("unrecognised directive: %" ++
> takeWhile (not.isSpace) s) s
> lexColon :: (Token -> P a) -> [Char] -> Int -> ParseResult a
> lexColon cont (':':rest) = returnToken cont (TokenKW TokDoubleColon) rest
> lexColon cont rest = returnToken cont (TokenKW TokColon) rest
> lexId :: (Token -> P a) -> Char -> String -> Int -> ParseResult a
> lexId cont c rest =
> readId rest (\ ident rest' -> returnToken cont (TokenInfo (c:ident) TokId) rest')
> lexChar :: (Token -> P a) -> String -> Int -> ParseResult a
> lexChar cont rest = lexReadChar rest
> (\ ident -> returnToken cont (TokenInfo ("'" ++ ident ++ "'") TokId))
> lexString :: (Token -> P a) -> String -> Int -> ParseResult a
> lexString cont rest = lexReadString rest
> (\ ident -> returnToken cont (TokenInfo ("\"" ++ ident ++ "\"") TokId))
> lexCode :: (Token -> P a) -> String -> Int -> ParseResult a
> lexCode cont rest = lexReadCode rest (0 :: Integer) "" cont
> lexNum :: (Token -> P a) -> Char -> String -> Int -> ParseResult a
> lexNum cont c rest =
> readNum rest (\ num rest' ->
> returnToken cont (TokenNum (stringToInt (c:num)) TokNum) rest')
> where stringToInt = foldl (\n c' -> digitToInt c' + 10*n) 0
> cleanupCode :: String -> String
> cleanupCode s =
> dropWhile isSpace (reverse (dropWhile isSpace (reverse s)))
This has to match for @}@ that are {\em not} in strings. The code
here is a bit tricky, but should work in most cases.
> lexReadCode :: (Eq a, Num a)
> => String -> a -> String -> (Token -> P b) -> Int
> -> ParseResult b
> lexReadCode s n c = case s of
> '\n':r -> \cont l -> lexReadCode r n ('\n':c) cont (l+1)
>
> '{' :r -> lexReadCode r (n+1) ('{':c)
>
> '}' :r
> | n == 0 -> \cont -> returnToken cont (TokenInfo (
> cleanupCode (reverse c)) TokCodeQuote) r
> | otherwise -> lexReadCode r (n-1) ('}':c)
>
> '"'{-"-}:r -> lexReadString r (\ str r' ->
> lexReadCode r' n ('"' : (reverse str) ++ '"' : c))
>
> a: '\'':r | isAlphaNum a -> lexReadCode r n ('\'':a:c)
>
> '\'' :r -> lexReadSingleChar r (\ str r' ->
> lexReadCode r' n ((reverse str) ++ '\'' : c))
>
> ch:r -> lexReadCode r n (ch:c)
>
> [] -> \_cont -> lexError "No closing '}' in code segment" []
----------------------------------------------------------------------------
Utilities that read the rest of a token.
> readId :: String -> (String -> String -> a) -> a
> readId (c:r) fn | isIdPart c = readId r (fn . (:) c)
> readId r fn = fn [] r
> readNum :: String -> (String -> String -> a) -> a
> readNum (c:r) fn | isDigit c = readNum r (fn . (:) c)
> readNum r fn = fn [] r
> isIdPart :: Char -> Bool
> isIdPart c =
> c >= 'a' && c <= 'z'
> || c >= 'A' && c <= 'Z'
> || c >= '0' && c <= '9'
> || c == '_'
> lexReadSingleChar :: String -> (String -> String -> a) -> a
> lexReadSingleChar (c:'\'':r) fn = fn (c:"'") r
> lexReadSingleChar ('\\':c:'\'':r) fn = fn ('\\':c:"'") r
> lexReadSingleChar r fn = fn "" r
> lexReadChar :: String -> (String -> String -> a) -> a
> lexReadChar ('\'':r) fn = fn "" r
> lexReadChar ('\\':'\'':r) fn = lexReadChar r (fn . (:) '\\' . (:) '\'')
> lexReadChar ('\\':c:r) fn = lexReadChar r (fn . (:) '\\' . (:) c)
> lexReadChar (c:r) fn = lexReadChar r (fn . (:) c)
> lexReadChar [] fn = fn "" []
> lexReadString :: String -> (String -> String -> a) -> a
> lexReadString ('"'{-"-}:r) fn = fn "" r
> lexReadString ('\\':'"':r) fn = lexReadString r (fn . (:) '\\' . (:) '"')
> lexReadString ('\\':c:r) fn = lexReadString r (fn . (:) '\\' . (:) c)
> lexReadString (c:r) fn = lexReadString r (fn . (:) c)
> lexReadString [] fn = fn "" []
> lexError :: String -> String -> Int -> ParseResult a
> lexError err = runP (lineP >>= \l -> fail (show l ++ ": " ++ err ++ "\n"))
> lexNestedComment :: Int -> ([Char] -> Int -> ParseResult a) -> [Char] -> Int
> -> ParseResult a
> lexNestedComment l cont r =
> case r of
> '-':'}':r' -> cont r'
> '{':'-':r' -> \line -> lexNestedComment line
> (\r'' -> lexNestedComment l cont r'') r' line
> '\n':r' -> \line -> lexNestedComment l cont r' (line+1)
> _:r' -> lexNestedComment l cont r'
> "" -> \_ -> lexError "unterminated comment" r l
|
