From 3a80fadcc82a4dd76e0d9b1356f4217e26cbcbd1 Mon Sep 17 00:00:00 2001
From: Lesenechal Remi <lesenechal.remi@gmail.com>
Date: Thu, 12 Mar 2020 17:32:49 +0100
Subject: [PATCH] rewrite interpreter recursion within the initial formalism.

---
 src/bin/expect_tests/ligo_interpreter_tests.ml |  4 +++-
 src/passes/6-interpreter/interpreter.ml        | 18 +++++++++---------
 src/stages/ligo_interpreter/types.ml           |  2 +-
 src/test/contracts/interpret_test.mligo        |  7 ++++++-
 4 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/bin/expect_tests/ligo_interpreter_tests.ml b/src/bin/expect_tests/ligo_interpreter_tests.ml
index 3dbf06bde..9a6069338 100644
--- a/src/bin/expect_tests/ligo_interpreter_tests.ml
+++ b/src/bin/expect_tests/ligo_interpreter_tests.ml
@@ -54,4 +54,6 @@ let%expect_test _ =
     val set_add = {  ; 0 = ({ ; 1 : int ; 2 : int ; 3 : int}) ; 1 = ({ ; 1 : int ; 2 : int ; 3 : int ; 4 : int}) ; 2 = ({ ; 1 : int}) }
     val set_iter_fail = "set_iter_fail" : failure
     val set_mem = {  ; 0 = (true) ; 1 = (false) ; 2 = (false) }
-    val recursion = 55 : int |}] ;
\ No newline at end of file
+    val recursion_let_rec_in = 55 : int
+    val sum_rec = <rec fun>
+    val top_level_recursion = 55 : int |}] ;
\ No newline at end of file
diff --git a/src/passes/6-interpreter/interpreter.ml b/src/passes/6-interpreter/interpreter.ml
index 96957225c..cdbee239c 100644
--- a/src/passes/6-interpreter/interpreter.ml
+++ b/src/passes/6-interpreter/interpreter.ml
@@ -272,25 +272,23 @@ and eval : Ast_typed.expression -> env -> value result
     match term.expression_content with
     | E_application ({expr1 = f; expr2 = args}) -> (
       let%bind f' = eval f env in
+      let%bind args' = eval args env in
       match f' with
       | V_Func_val (arg_names, body, f_env) ->
-        let%bind args' = eval args env in
         let f_env' = Env.extend f_env (arg_names, args') in
         eval body f_env'
-      | V_Func_rec (_fun_name,_fun_type,lambda, _env) ->
-        let%bind args' = eval args env in
-        let f_env' = Env.extend env (lambda.binder,args') in
-        eval lambda.result f_env'
+      | V_Func_rec (fun_name, arg_names, body, f_env) ->
+        let f_env' = Env.extend f_env (arg_names, args') in
+        let f_env'' = Env.extend f_env' (fun_name, f') in
+        eval body f_env''
       | _ -> simple_fail "trying to apply on something that is not a function"
     )
     | E_lambda {binder; result;} ->
       ok @@ V_Func_val (binder,result,env)
-    | E_recursive {fun_name; fun_type;lambda} ->
-      let env' = Env.extend env (fun_name, V_Func_rec(fun_name,fun_type,lambda,env)) in
-      ok @@ V_Func_rec (fun_name,fun_type,lambda,env')
-    | E_let_in { let_binder; rhs; let_result; _} ->
+    | E_let_in {let_binder ; rhs; let_result} -> (
       let%bind rhs' = eval rhs env in
       eval let_result (Env.extend env (let_binder,rhs'))
+    )
     | E_map kvlist | E_big_map kvlist ->
       let%bind kvlist' = bind_map_list
         (fun kv -> bind_map_pair (fun (el:Ast_typed.expression) -> eval el env) kv)
@@ -378,6 +376,8 @@ and eval : Ast_typed.expression -> env -> value result
       | _ -> simple_fail "not yet supported case"
         (* ((ctor,name),body) *)
     )
+    | E_recursive {fun_name; fun_type=_; lambda} ->
+      ok @@ V_Func_rec (fun_name, lambda.binder, lambda.result, env)
     | E_look_up _ ->
       let serr = Format.asprintf "Unsupported construct :\n %a\n" Ast_typed.PP.expression term in
       simple_fail serr
diff --git a/src/stages/ligo_interpreter/types.ml b/src/stages/ligo_interpreter/types.ml
index b9f9a7e5e..d2274e9ee 100644
--- a/src/stages/ligo_interpreter/types.ml
+++ b/src/stages/ligo_interpreter/types.ml
@@ -31,7 +31,7 @@ and constant_val =
 
 and value =
   | V_Func_val of (expression_variable * Ast_typed.expression * env)
-  | V_Func_rec of (expression_variable * Ast_typed.type_expression * Ast_typed.lambda * env)
+  | V_Func_rec of (expression_variable * expression_variable * Ast_typed.expression * env)
   | V_Ct of constant_val
   | V_List of value list
   | V_Record of value label_map
diff --git a/src/test/contracts/interpret_test.mligo b/src/test/contracts/interpret_test.mligo
index ebabbcf53..07932653e 100644
--- a/src/test/contracts/interpret_test.mligo
+++ b/src/test/contracts/interpret_test.mligo
@@ -233,9 +233,14 @@ let set_mem =
   Set.mem 4 s,
   Set.mem 1 (Set.empty : int set)
 
-let recursion =
+let recursion_let_rec_in =
   let rec sum : int*int -> int = fun ((n,res):int*int) ->
     let i = 1 in
     if (n<1) then res else sum (n-i,res+n)
   in
   sum (10,0)
+
+let rec sum_rec ((n,acc):int * int) : int =
+    if (n < 1) then acc else sum_rec (n-1, acc+n)
+
+let top_level_recursion = sum_rec (10,0)
\ No newline at end of file