Re: ending/stopping a script

[Dr . Jürgen Sauermann]

Hi,

see below.

Best Regards,
Jürgen

On 6/14/21 10:05 PM, enz...@gmx.com wrote:

Hi

every scripting language has a simple way to end script execution using code that 'reflects' the nature of the language's syntax - thus
bash - exit
python - exit
php - exit
perl - exit

If we take bash as example then there are actually 2 different ways to end a bash
script: exit and return. Although their effects look similar (both end the execution)
they are quite different: "exit" terminates the shell that executes the script (-process)
while "return" leaves the current script (-file) but does not terminate the process.

Compared to GNU APL this gives roughly the following relation:

GNU APL        bash
----------------------
)OFF        ←→ exit
]NEXTFILE   ←→ return

i thought as tempting as it is to use →/→0 to end a script would be nice - their use probably should be left specific for use in fns (real effect depends on )SI/)SIC)

There is a high risk of using →0 or → accidently, therefore I believe )OFF is a better solution.

and in keeping with the single character nature of apl - I suggest using '.' as first character on script line as way to end script\

I would argue that this single character nature - if it exists at all - applies only to the APL language
but not to the APL commands. I would consider the APL commands as belonging to the environment
in which the APL language itself lives and the syntax of that environment has always been different
from the syntax of the language.

And then, we already have )OFF and ]NEXTFILE, why reinvent the wheel?

using ⎕stop in an apl script doesn't keep to the character of apl coding

The purpose of ⎕STOP and ⎕TRACE seem to be to support the debugging of APL code.
So they wouldn't end up in production code. Manly languages have debugging facilities that
will only be used during coding and that will be removed when the code becomes mature.

On Mon, 14 Jun 2021 12:59:33 +0200
Dr. Jürgen Sauermann <m...@xn--jrgen-sauermann-zvb.de> wrote:

Hi,

actually N ⎕STOP B sets onr otr more breakpoints on line(s) N in the defined
function named B and it returns the current stop vector of the
functions. In my example,
the breakpoint is only reached if the dummy function STOP (you
can choose a different name if you prefer) is being called (in your script).

I noticed that ⎕STOP (which is an ISO standard construct) comes from
the time before APL scripting was introduced in GNU APL and for that
reason only works as expected in )SAVEd workspaces, but not so well
in )DUMPed ones. This is because after hitting the breakpoint the
interpreter returns to immediate execution mode.

However, in a )SAVEd workspace this means that the interpreter
reads the next input line comes from the user while in a )DUMPed
workspace the next input line comes from either the current script,
or from the next script, or from the user and therefore execution
will only stop in the last case but proceed in the first two cases,

This can be addressed in 3 ways:

Option A: fix ⎕STOP so that the current script will be stopped and input
is obtained (interactively) from the user (until the user issues ]NEXTFILE).

Option B: Add a new command, say ]PUSHFILE, which causes the interpreter
to read its input (interactively) from the user (until the user issues
]NEXTFILE).

Option C: leave things as they are.

Before implementing one of the options above I would like to receive some
feedback from the  GNU APL users regarding the way forward.

Best Regards,
Jürgen


On 6/13/21 7:33 PM, enz...@gmx.com wrote:

Hi


not sure exactly what to do here with the ⎕STOP code

  > cat script3

#! script3

'1 aaaaaa'

∇STOP
  'STOP CALLED'
∇

1 ⎕STOP 'STOP' ⍝ no output

'2 aaaaaa'

STOP  ⍝ outputs  STOP[1] but execution continues

'3 aaaaaa'

1 ⎕STOP STOP  ⍝ outputs STOP[1] but execution continues

'4 aaaaaa'

⍝ stops execution and ws stays open    outputs      IO_Files::open_next_file(): no more files
]NEXTFILE

'5 aaaaaa'

⍝ stops exeuction and ws stays open    outputs      IO_Files::open_next_file(): no more files
]nextfile

'6 aaaaaa'

/usr/local/bin/apl        loads clear ws

       )copy script3
DUMPED 2021-06-13  11:26:23 (GMT-6)
1 aaaaaa
2 aaaaaa
STOP[1]
3 aaaaaa
STOP[1]
4 aaaaaa
IO_Files::open_next_file(): no more files




On Sat, 12 Jun 2021 11:36:02 +0200
Dr. Jürgen Sauermann <m...@xn--jrgen-sauermann-zvb.de> wrote:

Hi,

]NEXTFILE would be my first choice also.

Alternatively you could think of defining a dummy function like:

∇STOP
  'STOP CALLED'
∇

and set ⎕STOP to its first line:

1 ⎕STOP 'STOP'

or so,

The difference is that ]NEXTFILE closes the script file, while
⎕STOP only stops execution (so you can continue execution
in the same script after making some changes).

Best Regards,
Jürgen



On 6/12/21 5:46 AM, Kacper Gutowski wrote:
On Fri, Jun 11, 2021 at 08:27:58PM -0600, enz...@gmx.com wrote:
)off ends the apl session completely - i want to keep the ws open and just end the script execytuib and then edit the script in directory (and move around the '→0' or what ever can end the script execution - for debug) and then )copy the edited script back into the ws and it runs until it hits the '→0'

Maybe something like ]NEXTFILE then.

-k