2 files changed, 28 insertions, 1 deletions
diff --git a/src/Identifiers.ml b/src/Identifiers.ml
index 21898498..cab1bafa 100644
--- a/src/Identifiers.ml
+++ b/src/Identifiers.ml
@@ -9,11 +9,14 @@ open Errors
 module type Id = sig
   type id
 
+  type generator
+  (** Id generator - simply a counter *)
+
   type 'a vector
 
   val zero : id
 
-  val incr : id -> id
+  val fresh : generator -> id * generator
 
   val to_string : id -> string
 
@@ -53,6 +56,8 @@ module IdGen () : Id = struct
   (* TODO: use Int64.t *)
   type id = int
 
+  type generator = id
+
   type 'a vector = 'a list
 
   let zero = 0
@@ -63,6 +68,8 @@ module IdGen () : Id = struct
      * they happen *)
     if x == max_int then raise (Errors.IntegerOverflow ()) else x + 1
 
+  let fresh gen = (gen, incr gen)
+
   let to_string = string_of_int
 
   let empty_vector = []
diff --git a/src/Interpreter.ml b/src/Interpreter.ml
index b8943a9a..3b16a1e3 100644
--- a/src/Interpreter.ml
+++ b/src/Interpreter.ml
@@ -1,6 +1,7 @@
 open Types
 open Values
 open Expressions
+open CfimAst
 open Print.Values
 open Errors
 
@@ -28,6 +29,25 @@ type config = { mode : interpreter_mode; check_invariants : bool }
 
 type outer_borrows = Borrows of BorrowId.Set.t | Borrow of BorrowId.id
 
+type stack_frame = { vars : var VarId.vector }
+(** A function frame
+
+    When using the interpreter in concrete mode (i.e, non symbolic) we
+    push a function frame whenever we enter a function body (and pop it
+    upon leaving it).
+ *)
+
+type eval_ctx = {
+  type_context : type_def TypeDefId.vector;
+  fun_context : fun_def FunDefId.vector;
+  type_vars : type_var TypeVarId.vector;
+  frames : stack_frame list;
+  env : env;
+  symbolic_counter : SymbolicValueId.generator;
+  borrows_counter : BorrowId.generator;
+}
+(** Evaluation context *)
+
 (** The following type identifies the relative position of expressions (in
     particular borrows) in other expressions.