* Instantiate: return a boolean

        For issue #30

src/python/ocarina-python_cmd.adb

@@ -129,8 +129,11 @@ package body Ocarina.Python_Cmd is
       Command : String)
    is
       pragma Unreferenced (Command);
+      Result : constant Boolean :=
+        Ocarina.Utils.Instantiate (Nth_Arg (Data, 1, ""));
+
    begin
-      Ocarina.Utils.Instantiate (Nth_Arg (Data, 1, ""));
+      Set_Return_Value (Data, Result);
    end On_Instantiate;
 
    ----------------------

src/python/ocarina-utils.adb

@@ -222,7 +222,8 @@ package body Ocarina.Utils is
    -- Instantiate --
    -----------------
 
-   procedure Instantiate (Root_System : String) is
+   function Instantiate (Root_System : String) return Boolean is
+      Success : Boolean;
    begin
       if Root_System /= "" then
          Root_System_Name := To_Lower
@@ -231,7 +232,12 @@ package body Ocarina.Utils is
       AADL_Root := Instantiate_Model (AADL_Root);
       if Present (AADL_Root) then
          Write_Line ("Model instantiated sucessfully");
+         Success := True;
+      else
+         Success := False;
       end if;
+
+      return Success;
    end Instantiate;
 
    --------------

src/python/ocarina-utils.ads

@@ -48,7 +48,7 @@ package Ocarina.Utils is
 
    procedure Load_AADL_File (Filename : String);
    function Analyze return Boolean;
-   procedure Instantiate (Root_System : String);
+   function Instantiate (Root_System : String) return Boolean;
    procedure Generate (Backend_Name : String);
    procedure Reset;