Re: Fun trick

On 1/14/2025 11:03 AM, Arne Vajhøj wrote:

On 1/13/2025 11:38 PM, Lawrence D'Oliveiro wrote:

On Mon, 13 Jan 2025 21:08:11 -0500, John Reagan wrote:

### They are probably most useful for modules, but why not allow
### them for programs?

Extended Pascal says only MODULEs so we just didn't
think about allowing them in PROGRAMs even though we allow [INITIALIZE].

>
Not sure what the point would be in having them in PROGRAMs, anyway.

 Definitely most useful for modules. I was just wondering
why not allow it in programs as well.
 It seems to have been explicit disallowed. The error message is:
 %PASCAL-E-TOPROGRAM, TO BEGIN/END DO not allowed in PROGRAM
 If one start to look for something useful then I would say that
TO BEGIN is just code after PROGRAM BEGIN, but TO END is more
than just code before PROGRAM END as it get triggered by other
program exits as well.
 Demo:
 $ type m.pas
module m(input,output);
 to begin do writeln('m to begin');
to end do writeln('m to end');
 end.
$ type p.pas
[inherit('m', 'sys$library:starlet')]
program p(input,output);
 [initialize]
procedure init;
 begin
    writeln('init');
end;
 procedure done;
 begin
    writeln('done');
end;
 var
    ent : integer64;
    desblk : array [1..4] of integer;
    cond : integer;
 begin
    writeln('begin');
    desblk[1] := 0;
    desblk[2] := iaddress(done);
    desblk[3] := 0;
    desblk[4] := iaddress(cond);
    $dclexh(desblk);
    $get_entropy(ent, 8);
    if (ent mod 2) = 0 then $exit(SS$_NORMAL);
    $canexh(desblk);
    writeln('end');
end.
$ pas/env m
$ pas p
$ link p + m
$ run p
m to begin
init
begin
end
m to end
$ run p
m to begin
init
begin
done
m to end
$ run p
m to begin
init
begin
end
m to end
$ run p
m to begin
init
begin
done
m to end
 Arne
 

I just looked.  The TO BEGIN/END DO was added back in 1987 by a former developer (not me).  I suspect that since the Extended Pascal standard only allows them in MODULEs, not PROGRAMs, that he just followed the draft standard at that point without considering that TO END DO is a little better than "code at the end".