Add Termination

Project2.fst

@@ -174,9 +174,23 @@ let rec nsteps n te cs =
 (* Our goal is to prove the termination of this function *)
 (* To this end, define a function the following function on callstacks that assigns a measure (in terms of a list of naturals that gets lexicographically interpreted) to each call stack *)
 
+val gas: plaincallstack -> Tot nat
+let gas cs =
+    match cs with
+        | (((gas, _, _, _), _, _)::_) -> gas
+        | _ -> 0
+
 val getDecArgList: (cs: callstack {wellformed cs}) -> Tot (list nat)
 let getDecArgList (cs: callstack {wellformed cs}) =
-  magic ()
+  [ (match cs with
+        | Exec ps -> gas ps
+        | Ter (HaltState _ _ g) _ -> g
+        | Ter ExcState _ -> 0)
+  ; size cs
+  ; match cs with
+    | Exec _ -> 1
+    | Ter _ _ -> 0
+  ]
 
 (* A simple helper function that converts a list to a lexicgraphical ordering *)
 val getLexFromList: (list nat) -> Tot (lex_t)