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105 lines
2.7 KiB
105 lines
2.7 KiB
module M = import "data/map.ml"
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module S = import "data/set.ml"
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open import "prelude.ml"
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open import "./lang.ml"
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open import "./lib/monads.ml"
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type addr =
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| Combinator of string
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| Arg of int
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type gm_code =
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| Push of addr
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| Update of int
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| Pop of int
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| Unwind
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| Mkap
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instance show gm_code begin
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let show = function
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| Mkap -> "Mkap"
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| Unwind -> "Unwind"
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| Push (Combinator k) -> "Push " ^ k
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| Push (Arg i) -> "Arg " ^ show i
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| Update n -> "Update " ^ show n
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| Pop n -> "Pop " ^ show n
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end
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let rec lambda_lift = function
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| Ref v -> pure (Ref v)
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| App (f, x) -> (| app (lambda_lift f) (lambda_lift x) |)
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| Lam (v, x) ->
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let! body = lambda_lift x
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let! (i, defs, known_sc) = get
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let vars =
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x |> free_vars
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|> S.delete v
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|> flip S.difference known_sc
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|> S.members
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let def = ("Lam" ^ show i, vars ++ [v], body)
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let app = foldl (fun f -> app f # Ref) (Ref ("Lam" ^ show i)) vars
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put (i + 1, Decl def :: defs, known_sc)
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|> map (const app)
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| Case (sc, alts) ->
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alts
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|> map (fun (_, x) -> x)
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|> foldl app sc
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|> lambda_lift
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let rec eta_contract = function
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| Decl (n, a, e) as dec ->
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match a, e with
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| [], _ -> dec
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| xs, App (f, Ref v) ->
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if v == last xs && not (S.member v (free_vars f)) then
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eta_contract (Decl (n, init a, f))
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else
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dec
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| _, _ -> dec
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| Data c -> Data c
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let rec lambda_lift_sc = function
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| Decl (n, a, e) ->
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match e with
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| Lam (v, e) -> lambda_lift_sc (Decl (n, a ++ [v], e))
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| _ ->
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let! e = lambda_lift e
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let! _ = modify (fun (a, b, s) -> (a, b, S.insert n s))
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pure (Decl (n, a, e))
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| Data c -> Data c |> pure
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type dlist 'a <- list 'a -> list 'a
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let rec compile (env : M.t string int) = function
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| Ref v ->
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match M.lookup v env with
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| Some i -> (Push (Arg i) ::)
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| None -> (Push (Combinator v) ::)
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| App (f, x) ->
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let f = compile env f
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let x = compile (map (1 +) env) x
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f # x # (Mkap ::)
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| Lam _ -> error "Can not compile lambda expression, did you forget to lift?"
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| Case _ -> error "Can not compile case expression, did you forget to lift?"
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let supercomb (_, args, exp) =
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let env = M.from_list (zip args [0..length args])
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let k = compile (M.from_list (zip args [0..length args])) exp
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k [Update (length env), Pop (length env), Unwind]
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let known_scs = S.from_list [ "getchar", "putchar" ]
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let program decs =
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let (decs, (_, lams, _)) =
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run_state (traverse (lambda_lift_sc # eta_contract) decs) (0, [], known_scs)
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flip map (lams ++ decs) @@ function
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| Decl ((nm, args, _) as sc) ->
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let code = supercomb sc
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(nm, length args, code)
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| Data _ -> error "data declaration in compiler"
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