adding string->symbol procedure

scheme.adb

@@ -756,6 +756,11 @@ procedure Scheme is
       return Make_String(Car(Arguments).all.Data.Symbol);
    end;
 
+   function String_To_Symbol_Proc (Arguments : Access_Object) return Access_Object is
+   begin
+      return Make_Symbol(Car(Arguments).all.Data.Strng);
+   end;
+
    procedure Init is
    begin
       The_Empty_List := Alloc_Object;
@@ -863,6 +868,9 @@ procedure Scheme is
       Define_Variable(Make_Symbol(To_Unbounded_String("symbol->string")),
                       Make_Primitive_Proc(Symbol_To_String_Proc'access),
                       The_Global_Environment);
+      Define_Variable(Make_Symbol(To_Unbounded_String("string->symbol")),
+                      Make_Primitive_Proc(String_To_Symbol_Proc'access),
+                      The_Global_Environment);
    end;
 
    -- READ ----------------------------------------------------------------