module RecCompiler where 

import Language.Haskell.Pretty

import Target
import RecType

comp :: Expr -> Target
comp (Const c)         = TUnitM c
comp (Var x)           = TUnitM (TVar x)
comp (Val (x, m) n)    = comp m `TBindM` TLambda1 x
                        (comp n)
comp (Let decls n)     = TLet (map (\ (x, m) -> let TUnitM c = comp m in (PVar x, c)) decls)
                              (comp n)
comp (App f x)         = comp f `TBindM` TLambda1 "_f"
                        (comp x `TBindM` TLambda1 "_x" 
                        (TApp1 (TVar "_f") (TVar "_x")))
comp (Lambda x m)      = TUnitM (if x=="_" then TLambda0 (comp m) else TLambda1 x (comp m)) 
comp (Delay m)         = TUnitM (comp m)
comp (If e1 e2 e3)     = comp e1 `TBindM` TLambda1 "_b" 
                        (TIf (TVar "_b") (comp e2) (comp e3))
comp (While e1 e2)     = TLet [(PVar "_while",  body)] (TVar "_while")
                 where body = comp e1 `TBindM`  TLambda1 "_b" 
                             (TIf (TVar "_b") (comp e2 `TBindM` TLambda0 (TVar "_while"))
                                              (TUnitM (TVar "()")))
comp (Begin [e])       = comp e 
comp (Begin (e:es))    = comp e `TBindM` TLambda0 
                        (comp (Begin es))


compDecls :: Decls -> [(Pattern, Target)]
compDecls decls =  map (\ (x, m) -> let TUnitM c = comp m in (PVar x, c)) decls