{ -- only list imports here import Char } %tokentype { Token } %lexer { lexer } { TokenEOF } %token 'b' { Sym _ } %% -- grammar taken from -- "Generalised LR Parsing in Haskell" -- Joao Fernandes, Joao Saraiva, and Joost Visser -- Universidade do Minho, Braga, Portugal -- submitted to AFP'04 summer school -- (Original source of grammar not identified by them) S : T {} T : A 'b' {} | T T T {} A : T 'b' A A A {} | T T 'b' {} | {} { data Token = TokenEOF | Sym Char | AnInt Int deriving (Show,Eq, Ord) lexer :: String -> [Token] lexer [] = [] lexer (' ':cs) = lexer cs lexer (c:cs) | c `elem` "+*-()" = Sym c : lexer cs lexer (c:cs) | isDigit c = let (yes,no) = span isDigit cs in AnInt (read $ c:yes) : lexer no }