LastXY Register for WP34S

[BarryMead]

(12-01-2014 06:45 PM)walter b Wrote:  Instead of LASTxy, I'd prefer an UNDO recalling the entire stack as it was before that erroneous last operation. KISS (but it has to be determined whether that's viable with the WP 34S).

It would be a really nice feature, if it turns out to be practical. So to determine if this potential feature is
practical requires answering the following questions (at least):
1. Where to store the stack? (Fewer general registers?) (Is undo more valuable than these registers?)
2. Is there sufficient flash memory to implement the "Undo" feature, and the implicit automatic save
features that would probably need to be incorporated into the setLastX() and setLastXY() routines
to make them available to all existing operators.
3. Is there a spot on the keyboard to put the "Undo" button (RCL CLx) might work because a partially
complete RCL operation can always be cancelled by the "EXIT" button. Or perhaps "f CLx" like on the 31s
since the CLP function could always be accessed through the "h PFCN" menu.
4. Verification that no existing programs (or very few) would be broken by the feature's implementation.
5. Does the demand for this feature warrant the effort to bring it into existence? What about the effort
to redo the keyboard overlays and change the manual? All of these weigh against such a big change.

Have I left out any milestones that would have to be evaluated to confirm the practicality of this potential
feature?