\begin{code}
module Lexer (identifier, reservedOp, parens, brackets) where

import Text.Parsec
import Text.Parsec.String
import qualified Text.Parsec.Token as P

language :: P.LanguageDef ()
language = P.LanguageDef {  P.commentStart     = "",
                            P.commentEnd       = "",
                            P.commentLine      = "",
                            P.nestedComments   = False,
                            P.identStart       = letter,
                            P.identLetter      = letter,
                            P.opStart          = parserZero,
                            P.opLetter         = parserZero,
                            P.reservedNames    = [],
                            P.reservedOpNames  = ["->"],
                            P.caseSensitive    = True}

lexer :: P.TokenParser ()
lexer = P.makeTokenParser language

identifier :: Parser String
identifier = P.identifier lexer

reservedOp :: String -> Parser ()
reservedOp = P.reservedOp lexer

parens :: Parser a -> Parser a
parens = P.parens lexer

brackets :: Parser a -> Parser a
brackets = P.brackets lexer
\end{code}