On Sat, Apr 16, 2011 at 10:29 AM, Nikhil A. Patil
doit :: DSL Term doit = do (+) <- (+) n0 <- n0 k <- k -- begin beautiful DSL code let x = k + n0 return $ x + x
I guess the core problem is that on each time you say '(+) <- (+)', you may actually get something different depending on what 'define_function' does. You say yourself that these functions change a hidden state. So, without any internal changes, I doubt you could do something better. One possible solution may be to have a special case for your Prelude functions and constants that never change. That is, if currently you have data Term = Term Key ... type Key = Integer and you store other informations about each term on your hidden state, then you may use data Term = Term Key ... data Key = Prelude Integer | User Integer Your define_* functions always return User keys, however now you can have unsafe versions of them that take a key as argument. Then your Prelude would be
module DSLPrelude where
(+) :: Term -> Term -> Term n0 :: Term k :: Term (+) = unsafe_define_function t1 "+" 2 n0 = unsafe_define_constant t2 "0" k = unsafe_define_constant t3 "k"
t1, t2, t3 :: Key (t1:t2:t3:_) = map Prelude [1..]
Of course, this is a lot of handwaving, but you haven't provided any details about your internal implementation. HTH, -- Felipe.