bug#3357: 23.0.93; Loss of undo info in calc

bug#3357: 23.0.93; Loss of undo info in calc

[Leo]

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

1. M-x calc
2. do some calculation for example: ' sqrt ( x ) RET a t x 5 RET
3. type q to quit calc
4. M-x calc to bring it back
5. type U

You will get "No further undo information is available".

I think this is a major inconvenience. For example, let's say in the
above example I subsitute x with some numerical value to get a result. I
think I have got what I want so I quit the window. But quite often I
need another result at a different x. When I bring back calc, I won't be
able to go back to the taylor series expression and have to start over.
The situation is even worse with curve fitting where you have to put in
the data points first.

Incidentally, I wonder whether making the two windows dedicated is more
desirable than current behaviour. I often end up with for example the
*Help* buffer showing up in the tiny "*Calc Trail*" window.

Thanks.

Leo

bug#3356: 23.0.93; Loss of undo info in calc

[Jay Belanger]

Leo <sdl.web@gmail.com> writes:
...
> 1. M-x calc
> 2. do some calculation for example: ' sqrt ( x ) RET a t x 5 RET
> 3. type q to quit calc
> 4. M-x calc to bring it back
> 5. type U
>
> You will get "No further undo information is available".

calc-quit sets the undo list to nil on purpose, probably to save limited
memory in the early days.   If there are still memory considerations,
then calc-quit could truncate the undo list rather than remove it,
otherwise it'd be easy to have calc-quit not do anything with the undo
list.

> Incidentally, I wonder whether making the two windows dedicated is more
> desirable than current behaviour.

Maybe, but I wonder if this would cause problems in some situations.
How would full-calc be affected, for instance.

Jay

bug#3356: 23.0.93; Loss of undo info in calc

[Leo]

On 2009-05-23 16:48 +0100, Jay Belanger wrote:
>> 1. M-x calc
>> 2. do some calculation for example: ' sqrt ( x ) RET a t x 5 RET
>> 3. type q to quit calc
>> 4. M-x calc to bring it back
>> 5. type U
>>
>> You will get "No further undo information is available".
>
> calc-quit sets the undo list to nil on purpose, probably to save limited
> memory in the early days.   If there are still memory considerations,
> then calc-quit could truncate the undo list rather than remove it,

I think it should do its best to protect user's data. This option seems
very desirable.

> otherwise it'd be easy to have calc-quit not do anything with the undo
> list.

-- 
.:  Leo  :.  [ sdl.web AT gmail.com ]  .: I use Emacs :.

bug#3356: 23.0.93; Loss of undo info in calc

[Leo]

On 2009-05-23 16:48 +0100, Jay Belanger wrote:
> Leo <sdl.web@gmail.com> writes:
> ...
>> 1. M-x calc
>> 2. do some calculation for example: ' sqrt ( x ) RET a t x 5 RET
>> 3. type q to quit calc
>> 4. M-x calc to bring it back
>> 5. type U
>>
>> You will get "No further undo information is available".
>
> calc-quit sets the undo list to nil on purpose, probably to save limited
> memory in the early days.   If there are still memory considerations,
> then calc-quit could truncate the undo list rather than remove it,
> otherwise it'd be easy to have calc-quit not do anything with the undo
> list.
>
>> Incidentally, I wonder whether making the two windows dedicated is more
>> desirable than current behaviour.
>
> Maybe, but I wonder if this would cause problems in some situations.
> How would full-calc be affected, for instance.
>
> Jay

It seems this bug can be closed.

-- 
Leo's Emacs uptime: 1 day, 15 hours, 20 minutes, 27 seconds