gistfile1.txt

{
module BF where
import List
}

%name bfParse
%tokentype { BFToken }
%error { BFParseError }

%token
	'+' {BFTokenIncrement}
	'-' {BFTokenDecrement}
	'[' {BFTokenLoopOB}
	']' {BFTokenLoopCB}
	',' {BFTokenRead}
	'.' {BFTokenWrite}
	'<' {BFTokenLeft}
	'>' {BFTokenRight}

%%
Exp: Symbol Exp {[$1] : $2} | Symbol {[$1]}

Symbol: '+' {BFSymbol $1}
	  | '-' {BFSymbol $1}
	  | '[' {BFSymbol $1}
	  | ']' {BFSymbol $1}
	  | '>' {BFSymbol $1}
	  | '<' {BFSymbol $1}
	  | ',' {BFSymbol $1}
	  | '.' {BFSymbol $1}

{
data Exp = BFSymbol BFToken

data BFToken = BFTokenIncrement
			 | BFTokenDecrement
			 | BFTokenLoopOB
			 | BFTokenLoopCB
			 | BFTokenRead
			 | BFTokenWrite
			 | BFTokenLeft
			 | BFTokenRight

BFParseError :: [BFToken] -> a
BFParseError _ = error "Parse error"

lexer :: String -> [BFToken]
lexer [] = []
lexer (c : string) = if (find (==c) "+-.,[]><") then (makeToken c) : (lexer string) else (lexer string)

makeToken :: Char -> BFToken
makeToken '+' = BFTokenIncrement
makeToken '-' = BFTokenDecrement
makeToken '[' = BFTokenLoopOB
makeToken ']' = BFTokenLoopCB
makeToken ',' = BFTokenRead
makeToken '.' = BFTokenWrite
makeToken '>' = BFTokenRight
makeToken '<' = BFTokenLeft

parse :: String -> exp
parse s = bfParse (lexer s)
}