-lex :: [Char] -> (Either String Token, [Char])
-lex [] = (Right EndOfFileToken, [])
-lex ['v':'a':'r':rest] = (Right VarToken, rest)
-lex ['V':'o':'i':'d':rest] = (Right VoidToken, rest)
-lex ['r':'e':'t':'u':'r':'n':rest] = (Right ReturnToken, rest)
-lex ['i':'f':rest] = (Right IfToken, rest)
-lex ['e':'l':'s':'e':rest] = (Right ElseToken, rest)
-lex ['w':'h':'i':'l':'e':rest] = (Right WhileToken, rest)
-lex ['T':'r':'u':'e':rest] = (Right TrueToken, rest)
-lex ['F':'a':'l':'s':'e':rest] = (Right FalseToken, rest)
-lex ['\'':'\\':x:'\'':rest] = case x of
- 'a' = (Right (CharToken (toChar 7)), rest) //Alarm
- 'b' = (Right (CharToken '\b'), rest) //Backspace
- 'f' = (Right (CharToken '\f'), rest) //Formfeed
- 'n' = (Right (CharToken '\n'), rest) //Newline
- 'r' = (Right (CharToken '\r'), rest) //Carriage Return
- 't' = (Right (CharToken '\t'), rest) //Horizontal tab
- 'v' = (Right (CharToken '\v'), rest) //Vertical tab
- _ = (Left ("Unknown escape: \\" +++ toString x), rest)
-lex ['\'':x:'\'':rest] = (Right (CharToken x), rest)
-lex [':':':':rest] = (Right DoubleColonToken, rest)
-lex ['<':'=':rest] = (Right LesserEqToken, rest)
-lex ['>':'=':rest] = (Right GreaterEqToken, rest)
-lex ['=':'=':rest] = (Right EqualsToken, rest)
-lex ['&':'&':rest] = (Right AmpersandsToken, rest)
-lex ['|':'|':rest] = (Right PipesToken, rest)
-lex ['-':'>':rest] = (Right ArrowToken, rest)
-lex ['(':rest] = (Right BraceOpenToken, rest)
-lex [')':rest] = (Right BraceCloseToken, rest)
-lex ['{':rest] = (Right CBraceOpenToken, rest)
-lex ['}':rest] = (Right CBraceCloseToken, rest)
-lex ['[':rest] = (Right SquareOpenToken, rest)
-lex [']':rest] = (Right SquareCloseToken, rest)
-lex [',':rest] = (Right CommaToken, rest)
-lex [':':rest] = (Right ColonToken, rest)
-lex [';':rest] = (Right SColonToken, rest)
-lex ['.':rest] = (Right DotToken, rest)
-lex ['+':rest] = (Right PlusToken, rest)
-lex ['-':rest] = (Right DashToken, rest)
-lex ['*':rest] = (Right StarToken, rest)
-lex ['/':rest] = (Right SlashToken, rest)
-lex ['%':rest] = (Right PercentToken, rest)
-lex ['=':rest] = (Right AssignmentToken, rest)
-lex ['<':rest] = (Right LesserToken, rest)
-lex ['>':rest] = (Right BiggerToken, rest)
-lex ['!':rest] = (Right ExclamationToken, rest)
-lex [x:xs]
-| isSpace x = lex xs
-| isDigit x
- # (is, rest) = span isDigit xs
- = (Right (NumberToken [x:is]), rest)
-| isAlpha x
- # (is, rest) = span (\c.isAlphanum c || c == '_') xs
- = (Right (IdentToken [x:is]), rest)
-| otherwise = (Left ("Unexpected character: " +++ toString x), [])