From 74df5ba0526545acae8d23350c41c45c9c480789 Mon Sep 17 00:00:00 2001
From: acondolu <andrea.condoluci@unibo.it>
Date: Thu, 14 Jun 2018 14:43:26 +0200
Subject: [PATCH] Implementing entanglement of terms

FIXME usage of flags b' in subst and mk_app
 must be understood and fixed!
---
 ocaml/simple.ml | 65 +++++++++++++++----------------------------------
 1 file changed, 20 insertions(+), 45 deletions(-)

diff --git a/ocaml/simple.ml b/ocaml/simple.ml
index a7a8d7a..5764c3c 100644
--- a/ocaml/simple.ml
+++ b/ocaml/simple.ml
@@ -9,14 +9,19 @@ open Pure
 type var = int;;
 type t =
  | V of var
- | A of bool * t * t
+ | A of (bool ref) * t * t
  | L of (bool * t)
 ;;
 
-let rec measure_of_t = function
- | V _ -> 0
- | A(b,t1,t2) -> (if b then 1 else 0) + measure_of_t t1 + measure_of_t t2
- | L(b,t) -> if b then measure_of_t t else 0
+let measure_of_t =
+ let rec aux acc = function
+ | V _ -> acc, 0
+ | A(b,t1,t2) ->
+   let acc, m1 = aux acc t1 in
+   let acc, m2 = aux acc t2 in
+   if not (List.memq b acc) && !b then b::acc, 1 + m1 + m2 else acc, m1 + m2
+ | L(b,t) -> if b then aux acc t else acc, 0
+ in snd ++ (aux [])
 ;;
 
 let string_of_t =
@@ -30,7 +35,7 @@ let string_of_t =
     | A _
     | L _ as t -> "(" ^ string_of_term_no_pars level t ^ ")"
   and string_of_term_no_pars_app level = function
-    | A(b,t1,t2) -> string_of_term_no_pars_app level t1 ^ (if b then "," else " ") ^ string_of_term_w_pars level t2
+    | A(b,t1,t2) -> string_of_term_no_pars_app level t1 ^ (if !b then "," else " ") ^ string_of_term_w_pars level t2
     | _ as t -> string_of_term_w_pars level t
   and string_of_term_no_pars level = function
     | L(_,t) -> "λ" ^ string_of_bvar level ^ ". " ^ string_of_term_no_pars (level+1) t
@@ -39,7 +44,7 @@ let string_of_t =
 ;;
 
 
-let delta = L(true,A(true,V 0, V 0));;
+let delta = L(true,A(ref true,V 0, V 0));;
 
 (* does NOT lift the argument *)
 let mk_lams = fold_nat (fun x _ -> L(false,x)) ;;
@@ -105,13 +110,13 @@ let rec subst b' level delift sub =
  function
  | V v -> if v = level + fst sub then lift level (snd sub) else V (if delift && v > level then v-1 else v)
  | L(b,t) -> L(b, subst b' (level + 1) delift sub t)
- | A(_,t1,(V v as t2)) when b' && v = level + fst sub ->
+ | A(_,t1,(V v as t2)) when !b' && v = level + fst sub ->
     mk_app b' (subst b' level delift sub t1) (subst b' level delift sub t2)
  | A(b,t1,t2) ->
     mk_app b (subst b' level delift sub t1) (subst b' level delift sub t2)
 and mk_app b' t1 t2 = if t1 = delta && t2 = delta then raise B
  else match t1 with
- | L(b,t1) -> subst (b' && not b) 0 true (0, t2) t1
+ | L(b,t1) -> subst (ref (!b' && not b)) 0 true (0, t2) t1
  | _ -> A (b', t1, t2)
 and lift n =
  let rec aux lev =
@@ -121,14 +126,14 @@ and lift n =
   | A (b,t1, t2) -> A (b,aux lev t1, aux lev t2)
  in aux 0
 ;;
-let subst = subst false 0 false;;
-let mk_app = mk_app true;;
+let subst = subst (ref false) 0 false;;
+let mk_app = mk_app (ref true);;
 
 let eta_eq =
  let rec aux t1 t2 = match t1, t2 with
   | L(_,t1), L(_,t2) -> aux t1 t2
-  | L(_,t1), t2 -> aux t1 (A(true,lift 1 t2,V 0))
-  | t1, L(_,t2) -> aux (A(true,lift 1 t1,V 0)) t2
+  | L(_,t1), t2 -> aux t1 (A(ref true,lift 1 t2,V 0))
+  | t1, L(_,t2) -> aux (A(ref true,lift 1 t1,V 0)) t2
   | V a, V b -> a = b
   | A(_,t1,t2), A(_,u1,u2) -> aux t1 u1 && aux t2 u2
   | _, _ -> false
@@ -244,36 +249,6 @@ let compute_max_lambdas_at hd_var j =
 
 let print_cmd s1 s2 = print_endline (">> " ^ s1 ^ " " ^ s2);;
 
-(* eat the arguments of the divergent and explode.
- It does NOT perform any check, may fail if done unsafely *)
-let eat p =
-print_cmd "EAT" "";
- let var, k = get_inert p.div in
- let phase = p.phase in
- let p =
-  match phase with
-  | `One ->
-      let n = 1 + max
-       (compute_max_lambdas_at var (k-1) p.div)
-       (compute_max_lambdas_at var (k-1) p.conv) in
-      (* apply fresh vars *)
-      let p, t = fold_nat (fun (p, t) _ ->
-        let p, v = freshvar p in
-        p, A(false, t, V (v + k))
-      ) (p, V 0) n in
-      let p = {p with phase=`Two} in
-      let t = A(false, t, delta) in
-      let t = fold_nat (fun t m -> A(false, t, V (k-m))) t (k-1) in
-      let subst = var, mk_lams t k in
-      let p = subst_in_problem subst p in
-      let _, args = get_inert p.div in
-      {p with div = inert_cut_at (args-k) p.div}
-  | `Two ->
-      let subst = var, mk_lams delta k in
-      subst_in_problem subst p in
- sanity p
-;;
-
 (* step on the head of div, on the k-th argument, with n fresh vars *)
 let step k n p =
  let var, _ = get_inert p.div in
@@ -281,10 +256,10 @@ print_cmd "STEP" ("on " ^ string_of_t (V var) ^ " (of:" ^ string_of_int n ^ ")")
  let p, t = (* apply fresh vars *)
   fold_nat (fun (p, t) _ ->
     let p, v = freshvar p in
-    p, A(false, t, V (v + k + 1))
+    p, A(ref false, t, V (v + k + 1))
   ) (p, V 0) n in
  let t = (* apply bound variables V_k..V_0 *)
-  fold_nat (fun t m -> A(false, t, V (k-m+1))) t (k+1) in
+  fold_nat (fun t m -> A(ref false, t, V (k-m+1))) t (k+1) in
  let t = mk_lams t (k+1) in (* make leading lambdas *)
  let subst = var, t in
  let p = subst_in_problem subst p in
-- 
2.39.2