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-- vim: et ts=2 sw=2 ai:
{-# LANGUAGE LambdaCase #-}
module SPL.Lex
where
import Prelude hiding(lex)
import Control.Applicative
import Control.Monad
import Data.Char
import Data.List.Utils
data Token
= TIdent String
| TInt Int
| TChar Char
| TBool Bool
| TParenOpen
| TParenClose
| TBrackOpen
| TBrackClose
| TBraceOpen
| TBraceClose
| TColonColon
| TEquals
| TSemicolon
| TDot
| TComma
| TArrow
| TIf
| TElse
| TWhile
| TReturn
| TVar
| TVoidType
| TCharType
| TBoolType
| TIntType
| TPlus
| TMinus
| TAsterisk
| TSlash
| TPercent
| TEqEq
| TLt
| TGt
| TLtEq
| TGtEq
| TExclamEq
| TAmpAmp
| TPipePipe
| TColon
| TExclam
| TSingleComment String
| TBlockComment String
deriving (Show, Eq)
isCommentToken :: Token -> Bool
isCommentToken (TSingleComment _) = True
isCommentToken (TBlockComment _) = True
isCommentToken _ = False
isIdentToken :: Token -> Bool
isIdentToken (TIdent _) = True
isIdentToken _ = False
lex :: (Monad m, Alternative m) => String -> m [Token]
lex [] = pure []
lex (c:s) | isSpace c = lex s
lex s = (comment s <|> item s <|> int s <|> char s <|> bool s <|> ident s) >>=
\(t,s') -> lex s' >>= \ts -> pure (t:ts)
where
ident :: (Alternative m) => String -> m (Token, String)
ident (c:s)
| isAlpha c = pure (TIdent (c:cs), s')
| otherwise = empty
where (cs,s') = span isIdentChar s
int :: (Alternative m) => String -> m (Token, String)
int (c:s)
| isDigit c = pure (TInt $ read (c:cs), s')
| otherwise = empty
where (cs,s') = span isDigit s
char :: (Alternative m) => String -> m (Token, String)
char ('\'':c:'\'':s) = pure (TChar c, s)
char _ = empty
bool :: (Alternative m) => String -> m (Token, String)
bool ('F':'a':'l':'s':'e':s) = noIdentifier (TBool False) s
bool ('T':'r':'u':'e':s) = noIdentifier (TBool True) s
bool _ = empty
comment :: (Alternative m) => String -> m (Token, String)
comment ('/':'/':s) = pure (TSingleComment cs, s')
where
(cs, s') = span (/= '\n') s
comment ('/':'*':s) = pure (TBlockComment cs, s')
where
(cs, _:_:s') = spanList (\case
('*':'/':s) -> False
_ -> True) s
comment _ = empty
item :: (Alternative m) => String -> m (Token, String)
item ('i':'f':s) = noIdentifier TIf s
item ('e':'l':'s':'e':s) = noIdentifier TElse s
item ('w':'h':'i':'l':'e':s) = noIdentifier TWhile s
item ('r':'e':'t':'u':'r':'n':s) = noIdentifier TReturn s
item ('v':'a':'r':s) = noIdentifier TVar s
item ('V':'o':'i':'d':s) = noIdentifier TVoidType s
item ('C':'h':'a':'r':s) = noIdentifier TCharType s
item ('B':'o':'o':'l':s) = noIdentifier TBoolType s
item ('I':'n':'t':s) = noIdentifier TIntType s
item ('=':'=':s) = pure (TEqEq, s)
item ('<':'=':s) = pure (TLtEq, s)
item ('>':'=':s) = pure (TGtEq, s)
item ('!':'=':s) = pure (TExclamEq, s)
item ('&':'&':s) = pure (TAmpAmp, s)
item ('|':'|':s) = pure (TPipePipe, s)
item (':':':':s) = pure (TColonColon, s)
item ('-':'>':s) = pure (TArrow, s)
item ('(':s) = pure (TParenOpen, s)
item (')':s) = pure (TParenClose, s)
item ('[':s) = pure (TBrackOpen, s)
item (']':s) = pure (TBrackClose, s)
item ('{':s) = pure (TBraceOpen, s)
item ('}':s) = pure (TBraceClose, s)
item ('=':s) = pure (TEquals, s)
item (';':s) = pure (TSemicolon, s)
item ('.':s) = pure (TDot, s)
item (',':s) = pure (TComma, s)
item ('+':s) = pure (TPlus, s)
item ('-':s) = pure (TMinus, s)
item ('*':s) = pure (TAsterisk, s)
item ('/':s) = pure (TSlash, s)
item ('%':s) = pure (TPercent, s)
item ('<':s) = pure (TLt, s)
item ('>':s) = pure (TGt, s)
item (':':s) = pure (TColon, s)
item ('!':s) = pure (TExclam, s)
item _ = empty
noIdentifier :: (Alternative m) => Token -> String -> m (Token, String)
noIdentifier t [] = pure (t, [])
noIdentifier t s@(c:_)
| isIdentChar c = empty
| otherwise = pure (t, s)
isIdentChar :: Char -> Bool
isIdentChar = liftM2 (||) isAlphaNum (== '_')
|
