Re: [Bug-apl] Can't break out of the middle on a display operation

[Juergen Sauermann]

Hi,

not so. I implemented ⎕SYL[⎕IO+26;] for that case. Just try:

      ⎕SYL[⎕IO+26]←2000
      ⍳1000000
      ...

/// Jürgen


On 07/09/2014 05:11 AM, Elias Mårtenson wrote:

Yeah, and neither would Jürgen. Seems like I was in the minority on that one. :-)

Regards,

Elias

On 9 July 2014 11:10, Blake McBride <address@hidden> wrote:

I wouldn't do that! 

On Tue, Jul 8, 2014 at 10:01 PM, Elias Mårtenson <address@hidden> wrote:

I suggested some time ago that very large data sets shouldn't be displayed at all, since they are not only slow, they are also largely useless in an interactive session.

It was decided that this approach would not be taken, but I don't remember the justification for it.

Regards,

Elias

On 9 July 2014 10:58, Blake McBride <address@hidden> wrote:

I think the layout function need two modifications:

1.  enable ^C

2.  at least for large data, output as you go rather than format the whole thing and then output the whole thing

--blake

On Tue, Jul 8, 2014 at 9:27 PM, Elias Mårtenson <address@hidden> wrote:

There is already the SIGINT signal which is processed by GNU APL to interrupt a function execution. However, this interruptability is not extended to the layout function.

On 9 July 2014 09:09, Peter Teeson <address@hidden> wrote:

In Sharp APL (IPSA) we had a "panic int" which interrupted whatever was being computed after a predetermined time.
It was inherent to the interpreter because we ran a timesharing system.
I don't recall the exact details but it went something like this;

1) Workspace gets swapped in for execution and is given a quantum of CPU time
2) At the end of that quantum a second but quite small (relative to the normal ) additional amount of CPU was allocated
 to see if that would allow an interrupt at a "suitable" point in the function/operation that was going on.
3) If that extra time was not sufficient the workspace was arbitrarily interrupted and AFAICR the user got )CLEAR WS.

That's probably not exactly correct (I never read the actual assembly code for that part of the interpreter).
But the idea worked for us.

On a single user system there is no real need for a specific quantum; the OS takes care of  scheduling.
But perhaps a "panic int" concept in some form or other might be useful?
Perhaps allowing the user to decide if they want to continue?
Perhaps with a default value? Perhaps assignable by the user?

respect…

Peter

On 2014-07-08, at 1:50 PM, Blake McBride <address@hidden> wrote:

> If I do:
>
>       z←⍳1000000
>
> the operation is very fast.  But if I do:
>
>       ⍳1000000
>
> it is very slow, presumably because it is formatting the whole thing for display.  No problem.
>
> The problem is that during its effort to format for display, I cannot use ^C.  ^C appears to work fine in normal situations - but not during the format for display time.  During format-for-display time ^C is ignored.
>
> This caused me a problem when I accidentally mis-typed something.  The mis-type caused something very large to be displayed.  In fact, it was so large that my machine started paging.  I was unable to use ^C to stop it.  After waiting an hour, I had to kill the process and loose my work.
>
> Thanks.
>
> Blake
>