Re: 5250 and un-do

Buck and Jon have already provided good responses, and cover the main
things. I have kind of a side comment:

On Sat, Dec 16, 2017 at 11:27 AM, Booth Martin <booth@xxxxxxxxxxxx> wrote:

My first thought is that I have to keep an array of changes and read them
back 1 at a time but this has got to be a wheel that is already invented?
The rest of the world has had repeat un-do for 30+ years.

As far as I know, and as far as I can tell from my own observations,
undo is (1) far from universal, even in Windows, and (2) quite ad-hoc
in implementation. It's not like there is some "undo library" that
Java or .NET programmers at large can import that magically confers
standardized undo capabilities. No doubt there are some common themes
and approaches that translate from application to application,
especially in today's era of open source, but every application that
offers undo still has to work out implementation details in their own
way, pretty much.

John Y.