DragginMath: Undo/Redo and History

DragginMath is a tool where you can experiment with algebra: try things out and see what happens. And when you have done something and looked at the result, you will sometimes decide that you really wanted to do something else. Or maybe you just want to see it happen again.

This is what the Undo ↩️ and Redo ↪️ buttons at the top of the screen are about.

You can undo as far back into a problem as you want to go, even back to the beginning. Then you can redo each step, seeing which mode was used and which nodes were involved. Or, at any point, you can strike out in a different direction and try something else. But once you do that, all steps going forward from that point are forgotten and can no longer be redone.

If you want to see the sequence of problems and steps, use the History ⬆️ button. This shows a different screen.

The top half of the History screen lists the starting points of your last 100 problems. The current problem is at the bottom of the list. When the 100 limit is reached, the oldest problem is automatically and quietly forgotten.

The bottom half of the History screen lists the sequence of steps for whatever problem is currently selected in the top half. There is no limit on the number of steps. Swipe up and down on either list as needed to show more.

Double-tap a problem in the top half to reload it from the beginning. Or double-tap a step in the bottom half to reload that problem at that step. However you select, you can then Redo ↪️ and Undo ↩️ your way through it again. If you decide not to make a selection, tap OK at the bottom to return to whatever you were doing before you tapped ⬆️.

Swipe left on a problem in the top list to expose the Delete button for that problem.

Swipe left on a step in the bottom list to expose the Annotate button for that step. Steps cannot be deleted.