Minor fixes to comments

src/macro/MacroBison.yy

@@ -228,7 +228,7 @@ comma_expr : %empty
            ;
 
 tuple_comma_expr : %empty
-                   { $$ = vector<MacroValuePtr>{}; } // Empty array
+                   { $$ = vector<MacroValuePtr>{}; } // Empty tuple
                  | expr COMMA
                    { $$ = vector<MacroValuePtr>{$1}; }
                  | expr COMMA expr

src/macro/MacroDriver.hh

@@ -165,7 +165,7 @@ private:
   vector<env_t> func_env;
 
   //! Stack used to keep track of (possibly nested) loops
-  //! First element is loop variable name
+  //! First element is loop variable name(s)
   //! Second is the array over which iteration is done
   //! Third is subscript to be used by next call of iter_loop() (beginning with 0) */
   stack<tuple<vector<string>, shared_ptr<ArrayMV>, int>> loop_stack;