While the idea of 'UNDO' seems simple, it is often significantly complex. The nature of predominant thinking in programming is linear, and moreover, one directional, i. e., programs start and go forward.
Try thinking about the everyday problem of following driving directions to a that new place you have never before visited. You have the instructions of the person who knows the route well. Start at A, go to B, turn left, go to C, turn right, go 2 miles, turn left, .... etc. Now in the midst of following those very explicit instructions you become suspicious that you are no longer on the directed path. So, just 'undo' your recent driving, or go back to your original starting location..... yeah, right, it is really simple. NOT! The APPLE Macintosh programming culture rigorously keeps an 'UNDO' capability for programs as a matter of corporate policy. To provide this 'UNDO' feature, it is said by Mac pro's that this often consumes about half of the programming effort of Macintosh applications. ...and, this high cost of 'UNDO' is experienced when the work starts out from the beginning with the commitment to support the 'UNDO' feature! In the driving example, most people begin the journey with the belief that an 'UNDO' action will be entirely unnecessary. ...think about it. This is not a trivial problem. It is not even a simple problem. ...and, the importance of solving this problem is often not appreciated until we are in the midst of needing the solution. ...which is, of course, often too late. richard, K5BWV P. S. I once received a monthly statement from Sears for over $2000 involving a purchase of a $5 item. How that came to be is another story. When Sears was asked to correct that erroneous transaction, I was compelled by their staff to return to the original point of sale at a time when the specific clerk who performed the original sale was present. That clerk had to enter a new point of sale transaction for an offsetting amount to clear the charge. No 'UNDO' was built into the Sears retail credit charge system! P. P. S. When the Apollo 13 journey to the Moon suffered a catastrophic power failure, recall that there was not any 'UNDO' capability present in that system. Imagine how costly and complex that 'UNDO' feature would have been. ...perhaps, even impossible. ..................... Rick Braun wrote: > Seems an easy thing to do with programs like HRD etc. > ----- Original Message ----- > From: Wes Stewart<mailto:n...@yahoo.com> > To: elecraft@mailman.qth.net<mailto:elecraft@mailman.qth.net> ; IIIEdward > Dickinson<mailto:softb...@windstream.net> > Sent: Saturday, October 24, 2009 6:20 PM > Subject: Re: [Elecraft] K3 Undo/Back Button..? > > > Boy, that's a good idea, even if it's only one step back. > > Wes N7WS > .. ... .... ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
