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|
--
-- Lexer for MicroC
--
-- Joćo Saraiva
-- 2002
--
module Funcs_Lexer where
import Data.Char
--
-- Tokens passed to the parser
--
data Token
= Tsemicolon
| TopenB
| TcloseB
| TopenSB
| TcloseSB
| TopenCB
| TcloseCB
| Ttowdots
| Tcomma
| Tequal
| Tand
| Tor
| Tassing
| Tadd
| Tmul
| Tsub
| Tdiv
| Tgt
| Tlt
| Tnot
| Ttrue
| Tfalse
| Tint
| Treal
| Tbool
| Tchar
| Tif
| Tthen
| Telse
| Twhile
| Tinput
| Tprint
| TIdent String
| TintVal Int
| TrealVal Float
deriving Show
lexer [] = []
lexer (';':cs) = Tsemicolon : lexer cs
lexer ('(':cs) = TopenB : lexer cs
lexer (')':cs) = TcloseB : lexer cs
lexer ('[':cs) = TopenSB : lexer cs
lexer (']':cs) = TcloseSB : lexer cs
lexer ('{':cs) = TopenCB : lexer cs
lexer ('}':cs) = TcloseCB : lexer cs
lexer (':':cs) = Ttowdots : lexer cs
lexer (',':cs) = Tcomma : lexer cs
lexer ('=':'=':cs) = Tequal : lexer cs
lexer ('&':'&':cs) = Tor : lexer cs
lexer ('|':'|':cs) = Tand : lexer cs
lexer ('=':cs) = Tassing : lexer cs
lexer ('+':cs) = Tadd : lexer cs
lexer ('*':cs) = Tmul : lexer cs
lexer ('-':cs) = Tsub : lexer cs
lexer ('/':cs) = Tdiv : lexer cs
lexer ('>':cs) = Tgt : lexer cs
lexer ('<':cs) = Tlt : lexer cs
lexer ('!':cs) = Tnot : lexer cs
lexer (c:cs)
| isSpace c = lexer cs
| isAlpha c = lexSTR (c:cs)
| isDigit c = lexINT (c:cs)
lexINT cs =
case span isDigit cs of
(var,rest) -> TintVal ((read var)::Int) : lexer rest
lexSTR cs =
case span isLegalChar cs of
("true",rest) -> Ttrue : lexer rest
("false",rest) -> Tfalse : lexer rest
("int",rest) -> Tint : lexer rest
("real",rest) -> Treal : lexer rest
("bool",rest) -> Tbool : lexer rest
("char",rest) -> Tchar : lexer rest
("if",rest) -> Tif : lexer rest
("then",rest) -> Tthen : lexer rest
("else",rest) -> Telse : lexer rest
("while",rest) -> Twhile : lexer rest
("input",rest) -> Tinput : lexer rest
("print",rest) -> Tprint : lexer rest
(var,rest) -> TIdent var : lexer rest
isLegalChar c = let x = ord c
in (isAlpha c) || (isDigit c) || (c == '_')
runScan = do s <- readFile "input"
let t = lexer s
putStr (show t)
return () -- (scanner inp))
|
