Re: libapl question

[Chris Moller]

    Many thanks for the quick fix.
      
      As to the ⍎ issue, I'm using libapl in
      a limited context as an embedded _expression_ evaluator and not as a
      full-fledged APL environment, so maybe the issue won't bite me.  I
      expect I'll find out later today.
      
      Thanks again,
      Chris

On 1/1/21 7:24 AM, Dr. Jürgen Sauermann wrote:

>       
>       Hi Chris,
>         
>         fixed in SVN 1400.
>         
>         However, please note the following:
>         
>         In GNU APL, you may, in principle, execute commands with ⍎ which
>         is a non-standard
>         APL extension. I have tested your case with both ⍎')LOAD
>           wsname' and
>         with  ⍎')COPY
>             wsname'
>           instead of libapl. The first test failed while
>       the second case succeeded.
>       
>       The reason why the first case failed was because ⍎ of commands is
>       only
>       allowed for commands that do not modify the )SI stack
>       (otherwise
>       hell would brake loose). Now, )LOAD modifies the )SI
>       stack while )COPY
>       does not. Since not allowing )LOAD would be somewhat
>       weird, it
>       is not entirely rejected, but does an automatic )SIC
>       before it is being executed.
>       This )SIC is necessary (since after it a )LOAD does no longer
>       modify the )SI stack)
>       but invisible to the user. As a consequence, the result of an
>       assignment like
>       Q←⍎')LOAD wsname' gets lost because an error
>         occurs before the assignment takes place
>         and right after the error the )SI stack is cleared
>         (which hides the error from the user).
>         
>         I suppose that libapl behaves somewhat differently
>         because it performs the command
>         directly instead of using ⍎, but the problem remains the same.
>         The assignment of the
>         )LOAD command output is done in the old workspace which is
>         )CLEARed before
>         the )LOAD proceeds and may therefore be lost. The
>         commands which do an automatic
>         )SIC are: )LOAD, )QLOAD, )CLEAR
>         (aka. )RESET) and )SIC.
>         
>         Best Regards,
>         Jürgen
>       
>       
>       On 12/31/20 8:59 PM, Chris Moller wrote:
> >         
> >         Being some combination of sadistic and
> >           masochistic, I'm trying to use the libapl library using the
> >           libapl.h API
> >           
> >           libapl.h says 
> >         
> > > /// Pass `command`
> > >             to the command processor and return its output.
> > >             extern const char * apl_command(const char *
> > >               command_utf8);
> > >         
> >         but when I do 
> >         
> > > const char *rc =
> > >             apl_command (")load workspace");
> > >         
> >         it dumps 
> >         
> > > SAVED
> > >               2020-12-30 17:18:13 (GMT-4)
> > >         
> >         to stdout and rc is empty.
> >         
> >         Am I doing something wrong, or am I trying to do something APL
> >         was never intended to do?  I'd like to be able to capture
> >         everything libapl says and not have it go to stdout/stderr.
> >         
> >         --cm
> >       
>       
>