lex.icl

   1 implementation module lex
   2
   3 import Control.Monad
   4 import Data.Either, Data.Maybe, Data.Map, Data.Func
   5 import StdString
   6 import StdTuple
   7 import StdBool
   8 import StdList
   9 import StdChar
  10
  11 SingleCharTokens :: Map Char TokenValue
  12 SingleCharTokens = fromList [
  13         ('(', BraceOpenToken), (')', BraceCloseToken), ('{', CBraceOpenToken),
  14         ('}', CBraceCloseToken), ('[', SquareOpenToken), (']', SquareCloseToken),
  15         (',', CommaToken), (':', ColonToken), (';', SColonToken),
  16         ('.', DotToken), ('+', PlusToken), ('*', StarToken), ('/', SlashToken),
  17         ('%', PercentToken), ('=', AssignmentToken), ('<', LesserToken),
  18         ('>', BiggerToken), ('!', ExclamationToken)]
  19
  20 EscapeMap :: Map Char Char
  21 EscapeMap = fromList [('a', toChar 7), ('b', '\b'), ('f', '\f'), ('n', '\n'),
  22         ('r', '\r'), ('t', '\t'), ('v', '\v')]
  23
  24 lexer :: [Char] -> LexerOutput
  25 lexer x = lexer` x 1
  26         where
  27                 lexer` :: [Char] Int -> LexerOutput
  28                 lexer` [] i = Right []
  29                 lexer` x i = case lex x i of
  30                         (Right t, rest, i) = lexer` rest i >>= \ts.Right [t:ts]
  31                         (Left e, _, _) = Left e
  32
  33 ret:: TokenValue [Char] Int -> (Either String Token, [Char], Int)
  34 ret tv rest i = (Right (i, tv), rest, i)
  35
  36 err :: String Int -> (Either String Token, [Char], Int)
  37 err s i = (Left ("Line " +++ toString i +++ ": " +++ s), [], i)
  38
  39 lex :: [Char] -> (Int -> (Either String Token, [Char], Int))
  40 lex [] = ret EndOfFileToken []
  41 lex ['/':'/':xs] = lex (dropWhile ((<>) '\n') xs)
  42 lex ['/':'*':xs] =  \i.let (c, r) = span ((<>) ('*','/')) $ zip2 [' ':xs] xs in
  43         lex (tl $ map snd $ tl $ r) (i + length [x\\(x, _)<-c | x == '\n'])
  44 lex ['v':'a':'r':xs] = ret VarToken xs
  45 lex ['V':'o':'i':'d':xs] = ret VoidToken xs
  46 lex ['r':'e':'t':'u':'r':'n':xs] = ret ReturnToken xs
  47 lex ['i':'f':xs] = ret IfToken xs
  48 lex ['e':'l':'s':'e':xs] = ret ElseToken xs
  49 lex ['w':'h':'i':'l':'e':xs] = ret WhileToken xs
  50 lex ['T':'r':'u':'e':xs] = ret TrueToken xs
  51 lex ['F':'a':'l':'s':'e':xs] = ret FalseToken xs
  52 lex ['I':'n':'t':xs] = ret IntTypeToken xs
  53 lex ['C':'h':'a':'r':xs] = ret CharTypeToken xs
  54 lex ['B':'o':'o':'l':xs] = ret BoolTypeToken xs
  55 lex [':':':':xs] = ret DoubleColonToken xs
  56 lex ['!':'=':xs] = ret NotEqualToken xs
  57 lex ['<':'=':xs] = ret LesserEqToken xs
  58 lex ['>':'=':xs] = ret GreaterEqToken xs
  59 lex ['=':'=':xs] = ret EqualsToken xs
  60 lex ['&':'&':xs] = ret AmpersandsToken xs
  61 lex ['|':'|':xs] = ret PipesToken xs
  62 lex ['-':'>':xs] = ret ArrowToken xs
  63 lex ['\'':x:'\'':xs] = ret (CharToken x) xs
  64 lex ['\'':'\\':x:'\'':xs] = case get x EscapeMap of
  65         Just t = ret (CharToken t) xs
  66         _ = err ("Unknown escape: \\" +++ toString x)
  67 lex ['-':t=:[x:xs]]
  68 | isDigit x = let (n, r) = span isDigit t in
  69         ret (NumberToken (toInt $ toString ['-':n])) r
  70 | otherwise = ret DashToken  xs
  71 lex t=:[x:xs] = case get x SingleCharTokens of
  72         (Just tok) = ret tok xs
  73         Nothing
  74         | x == '\n' = \i.lex xs (i+1)
  75         | isSpace x = lex xs
  76         | isDigit x = let (v, r) = span isDigit t in
  77                 ret (NumberToken (toInt $ toString v)) r
  78         | isAlpha x = let (v, r) = span isIdent t in ret (IdentToken v) r
  79                 with isIdent c = isAlphanum c || c == '_'
  80         | otherwise = err ("Unexpected character: " +++ toString x)