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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% Frown --- An LALR(k) parser generator for Haskell 98 %
% Copyright (C) 2001-2005 Ralf Hinze %
% %
% This program is free software; you can redistribute it and/or modify %
% it under the terms of the GNU General Public License (version 2) as %
% published by the Free Software Foundation. %
% %
% This program is distributed in the hope that it will be useful, %
% but WITHOUT ANY WARRANTY; without even the implied warranty of %
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the %
% GNU General Public License for more details. %
% %
% You should have received a copy of the GNU General Public License %
% along with this program; see the file COPYING. If not, write to %
% the Free Software Foundation, Inc., 59 Temple Place - Suite 330, %
% Boston, MA 02111-1307, USA. %
% %
% Contact information %
% Email: Ralf Hinze <ralf@cs.uni-bonn.de> %
% Homepage: http://www.informatik.uni-bonn.de/~ralf/ %
% Paper mail: Dr. Ralf Hinze %
% Institut für Informatik III %
% Universität Bonn %
% Römerstraße 164 %
% 53117 Bonn, Germany %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%-------------------------------= --------------------------------------------
\section{The type of tokens}
%-------------------------------= --------------------------------------------
> module Lexer2
> where
> import Prelude
> import Data.Char
> import System.IO
> import Control.Monad
> import Base
> import Options
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\subsection{The |Token| type}
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
> data Token = White String
> | Comment String
> | Nested String
> | Conid String
> | Varid String
> | Consym String
> | Varsym String
> | Numeral String
> | Char String
> | String String
> | Comma
> | Semicolon
> | LeftParen
> | RightParen
> | LeftBracket
> | RightBracket
> | LeftCurly
> | RightCurly
> | Backquote
> | LeftSpecial
> | RightSpecial
> | EOF
> deriving (Eq, Ord, Show)
> isVarid, isConid, isWhite :: Token -> Bool
> isVarid (Varid _) = True
> isVarid _ = False
>
> isConid (Conid _) = True
> isConid _ = False
>
> isWhite (White _) = True
> isWhite (Comment _) = True
> isWhite (Nested _) = True
> isWhite _ = False
> toString :: Token -> String
> toString (White s) = s
> toString (Comment s) = "--" ++ s
> toString (Nested s) = "{-" ++ s ++ "-}"
> toString (Conid s) = s
> toString (Varid s) = s
> toString (Consym s) = s
> toString (Varsym s) = s
> toString (Numeral s) = s
> toString (Char s) = s
> toString (String s) = s
> toString Comma = ","
> toString Semicolon = ";"
> toString LeftParen = "("
> toString RightParen = ")"
> toString LeftBracket = "["
> toString RightBracket = "]"
> toString LeftCurly = "{"
> toString RightCurly = "}"
> toString Backquote = "`"
> toString LeftSpecial = "%{"
> toString RightSpecial = "}%"
> toString EOF = "<end of input>"
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\subsection{Some helper functions}
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
> lexFracExp :: String -> Maybe (String, String)
> lexFracExp s = do t <- match "." s
> (ds, u) <- lexDigits' t
> (e, v) <- lexExp u
> return ('.' : ds ++ e, v)
> `mplus` return ("", s)
>
> lexExp :: String -> Maybe (String, String)
> lexExp (e : s)
> | e `elem` "eE" = do (c : t) <- return s
> if c `elem` "+-" then return () else mzero
> (ds, u) <- lexDigits' t
> return (e : c : ds, u)
> `mplus` do (ds, t) <- lexDigits' s
> return (e : ds, t)
> lexExp s = return ("", s)
>
> lexDigits' :: String -> Maybe (String, String)
> lexDigits' s = do (cs@(_ : _), t) <- return (span isDigit s)
> return (cs, t)
> match :: String -> String -> Maybe String
> match p s
> | p == t = Just u
> | otherwise = Nothing
> where (t, u) = splitAt (length p) s
> nested :: Int -> String -> (String, String)
> nested _ [] = ([], [])
> nested 0 ('-' : '}' : s) = ([], '-':'}':s)
> nested n ('-' : '}' : s) = '-' <| '}' <| nested (n - 1) s
> nested n ('{' : '-' : s) = '{' <| '-' <| nested (n + 1) s
> nested n (c : s) = c <| nested n s
> lexCharLit, lexStrLit :: String -> (String, String)
> lexCharLit [] = ([], [])
> lexCharLit ('\'' : s) = ([], '\'' : s)
> lexCharLit ('\\' : c : s) = '\\' <| c <| lexCharLit s
> lexCharLit (c : s) = c <| lexCharLit s
>
> lexStrLit [] = ([], [])
> lexStrLit ('"' : s) = ([], '"' : s)
> lexStrLit ('\\' : c : s) = '\\' <| c <| lexStrLit s
> lexStrLit (c : s) = c <| lexStrLit s
> isSymbol, isIdChar :: Char -> Bool
> isSymbol c = c `elem` "!@#$%&*+./<=>?\\^|:-~"
> isIdChar c = isAlphaNum c || c `elem` "_'"
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