ANN: Sudoku Assistant

[Alex Tweedly]

Dan Shafer wrote:

> I'm doing something wrong or misunderstanding how the assistant works  
> or something.
>
> On Puzzle #1, I got to the place where I have five uncompleted cells.  
> One of them has a "?" which I think means there's an error somewhere.  
> But neither it nor the cell underneath it show any potential values  
> when I click on them. Then I click on an adjoining square to the one  
> without a "?" and select a value. Odds go to 0, so I know I've got a  
> wrong value there. I "Undo" and now I have three squares -- the two  
> original and the one I just undid -- that show no values to pick from  
> when I click on them. SO essentially, even though I think I could  
> solve the puzzle at this point, the assistant won't let me proceed.
>
> Bug? Something I'm not grokking?

One bug, one not-yet-implemented feature and maybe something you weren't 
fully grokking. (And for all I know, more bugs still to come ....)

The bug I found and fixed was in undo-ing after there were squares for 
which no value remained possible. Although they showed on-screen as a 
"?", the "?" wasn't being saved in the Undo/Redo state, so subsequent 
"Undo"s could leave blank squares.

I'm not sure how that led to the problem you described to me - so I've 
also added an automatic logging facility. All actions are logged (to a 
custom property), and there is a new menu item - File / Save Log File 
...   which will save the log file. So if anyone encounters strange 
situation, they can simply save the log file and email it to me.

The not-yet-implemented feature is that it ought to stop you assigning 
values to any more squares once any square has no remaining possible 
values.  I will add that - but in the mean time, keep an eye on the 
number of possibilities, and if it reaches 0 then you will need to Undo 
(one or more times), so you may as well do it immediately.  (I figure if 
you had fully grokked things, you wouldn't have continued ....)

Ver 1.3 has been uploaded to RevOnline, with these two changes.

Ver 1.4 will come later today, with an additional feature of showing a 
detailed breakdown of a single step (i.e. which squares change and why), 
which will be a useful way to see what the Assistant is doing for you 
(and indirectly to check that it does the right thing).  That info is 
actually already gathered in the log file, but I'm looking for a 
graphical way to show it.

And this is actually being much more interesting than I had expected - 
so there may well be a Version 2 that eliminates some of the cruft that 
has sprung up in the various  Ver 1.x's as it has grown organically.

-- 
Alex Tweedly       http://www.tweedly.net



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