note description: "Concrete version of an external iteration cursor for {READABLE_INDEXABLE}." library: "EiffelBase: Library of reusable components for Eiffel." status: "See notice at end of class." legal: "See notice at end of class." date: "$Date: 2017-02-09 12:11:51 +0000 (Thu, 09 Feb 2017) $" revision: "$Revision: 99809 $" class READABLE_INDEXABLE_ITERATION_CURSOR [G] inherit TYPED_INDEXABLE_ITERATION_CURSOR [G, READABLE_INDEXABLE [G]] create make feature {NONE} -- Initialization make (t: like target) -- Initialize cursor for target t. require t_attached: attached t do target := t if attached {VERSIONABLE} t as l_versionable then version := l_versionable.version else version := 0 end step := 1 is_reversed := False ensure target_set: target = t is_valid: is_valid default_step: step = 1 ascending_traversal: not is_reversed end feature -- Access cursor_index: INTEGER_32 -- Index position of cursor in the iteration. do Result := ((target_index - first_index).abs + step - 1) // step + 1 end target_index: INTEGER_32 -- Index position of target structure for current iteration. first_index: INTEGER_32 -- First valid index of target structure for current iteration. -- Note that if is_reversed, first_index might be greater than last_index. last_index: INTEGER_32 -- Last valid index of target structure for current iteration. -- Note that if is_reversed, first_index might be greater than last_index. step: INTEGER_32 -- Distance between successive iteration elements. new_cursor: like Current -- Restarted cursor of the iteration. do Result := twin Result.start end reversed alias "-": like Current -- Reversed cursor of the iteration. do Result := twin Result.reverse end incremented alias "+" (n: like step): like Current -- Cursor for the iteration with step increased by n. do Result := twin Result.set_step (step + n) end decremented alias "-" (n: like step): like Current -- Cursor for the iteration with step decreased by n. do Result := twin Result.set_step (step - n) end with_step (n: like step): like Current -- Cursor for the iteration with step set to n. do Result := twin Result.set_step (n) end feature -- Measurement version: NATURAL_32 -- Current version. note option: transient attribute end feature -- Status report after: BOOLEAN -- Are there no more items to iterate over? do Result := not is_valid or not target.valid_index (target_index) end is_reversed: BOOLEAN -- Are we traversing target structure backwards? is_valid: BOOLEAN -- Is the cursor still compatible with the associated underlying object? do Result := attached {VERSIONABLE} target as l_versionable implies l_versionable.version = version end is_first: BOOLEAN -- Is cursor at first position? do Result := target_index = first_index and then is_valid end is_last: BOOLEAN -- Is cursor at last position? do Result := target_index = last_index and then is_valid end feature -- Status setting reverse -- Flip traversal order. do is_reversed := not is_reversed ensure is_reversed: is_reversed = not old is_reversed end set_step (v: like step) -- Set increment step to v. require v_positive: v > 0 do step := v ensure step_set: step = v end feature -- Cursor movement start -- Move to first position. local l_target: like target do l_target := target if is_reversed then first_index := l_target.upper last_index := l_target.lower else last_index := l_target.upper first_index := l_target.lower end target_index := first_index end forth -- Move to next position. do if is_reversed then target_index := target_index - step else target_index := target_index + step end ensure then cursor_index_advanced: cursor_index = old cursor_index + 1 end feature {TYPED_INDEXABLE_ITERATION_CURSOR} -- Access target: READABLE_INDEXABLE [G] -- Associated structure used for iteration. note copyright: "Copyright (c) 1984-2017, Eiffel Software and others" license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)" source: "[ Eiffel Software 5949 Hollister Ave., Goleta, CA 93117 USA Telephone 805-685-1006, Fax 805-685-6869 Website http://www.eiffel.com Customer support http://support.eiffel.com ]" end -- class READABLE_INDEXABLE_ITERATION_CURSOR
Generated by ISE EiffelStudio