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Re: [Bug-apl] ⎕TRACE usage ?

From: Kacper Gutowski
Subject: Re: [Bug-apl] ⎕TRACE usage ?
Date: Fri, 23 Oct 2015 06:57:40 +0200

On Fri, Oct 23, 2015 at 5:45 AM,  <address@hidden> wrote:
> Is there documentation on how to use ⎕TRACE ? I ran info apl | grep ⎕TRACE
> and found nothing. It does not look like it is listed in the IBM APL2 manual
> either.

⎕STOP and ⎕TRACE are defined in ISO 13751.  They are part of
optional facility "Trace and Stop control." They allow setting up
some lines of defined function to print debug info or to suspend
execution when hit.

It's essentially the same as S∆ and T∆ which you can find in APL2
manual.  The difference is that while in APL2 you assign vector
of line numbers to specially named variables S∆fun and T∆fun to
set stop or trace on the function named fun, these are regular
system commands that take function name as a string argument.

Z ← ⎕TRACE 'name'   ←→  Z ← T∆name
A ⎕TRACE 'name'     ←→  T∆name ← A
Z ← ⎕STOP 'name'    ←→  Z ← S∆name
A ⎕STOP 'name'      ←→  S∆name ← A

HOWEVER I just found that GNU APL has arguments reversed in
dyadic case (setting lines to trace or stop on).

I think that's a bug.


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