-- Parser for fully paranthesized lambda terms

import Parser

data Expr = Id String | App Expr Expr | Lam String Expr
            deriving Show

expr :: Parser Expr
expr  =
 id >>> Id
 |||
 (ch '(' *** expr *** expr *** ch ')')
   >>> (\(_,(e1,(e2,_))) -> App e1 e2)
 |||
 (ch '(' *** ch '\\' *** id *** ch '.' *** expr *** ch ')')
   >>> (\(_,(_,(x,(_,(e,_))))) -> Lam x e)
 where
   ch c  =  sp (char c)
   id    =  sp ident