You are right, that undo/redo in Mathematica could be much more complicated than in for example text editor. But undo/redo is not the question of inversion of mathematical operations, but simply of conservating the state of the computer before each operation and simple returning that state back when undo/redo is needed.
Do you thing, that it is simple for example to return operation in Photoshop, when I'm editing nearly 1GB large image (in the area of the 360 deg. panoramas, I'm playing with, it is not an unusual size)?
And Photoshop has not only perfectly working undo/redo (like many other programs) but even very mature history tools, which can do much more with the deep history of operations. Many of such image operations are also pretty difficult and ireversibile mathematical algorithms.
So I realy don't understand, why undo/redo in Mathematica is so poor.
> -----Original Message----- > From: Bill Rowe [mailto:firstname.lastname@example.org] > Sent: Sunday, May 01, 2011 12:23 PM > To: email@example.com > Subject: Re: Undo/Redo > > On 4/30/11 at 5:53 AM, firstname.lastname@example.org (Barak Shoshany) wrote: > > >This seems to be a recurring subject in this group. > > >Mathematica is now at version 8 and there's still no multiple undo > >and redo functionality. I don't understand how such an amazing piece > >of software can lack such a trivial feature. Why isn't Woflram doing > >anything about it? Heck, I'll even write the code for undo/redo > >myself for them for free if they let me. Is there someone at Wolfram > >I can complain on the matter? Perhaps an internet petition is in > >order? What do you think? > > Simply put, implementation of undo/redo for something like > Mathematica is far more complex than you suggest. > > Undo/redo in a text editor or word processor is manipulating > what I will call static text, i.e., text that is to be > read/printed etc that does not change the state of your machine, > it not executed. This isn't the case for Mathematica. > > You really need to think about what you mean by say undo in the > context of Mathematica. What does it mean to undo a computation? > Keep in mind, many mathematical operations have no simple inverse. > > Reverting the state of a text document to a previous state is > quite simple compared to doing the same for a Mathematica session.