Re: libapl apl_exec results displayed as ?

[Chris Moller]

    Yeah, I don't understand a path from a result code
      integer to a stdout character, which is why I suspect there's
      something going on in the freepascal-C interface.  Many years ago,
      I worked with a Java-to-C interface which was not
      straight-forward.  Maybe the freepascal-C interface is similarly
      weird.

On 7/25/22 11:46, Dr. Jürgen Sauermann wrote:

Hi,

0 is an error code, pretty much ⎕ET on page 287 of the APL language reference. The major error code, i.e. ↑⎕ET,
is the same as in APL2, the minor error code 1↓⎕ET may differ. It has no relation to ⎕IO.

I can't currently see how the result code would make its way to stdout, maybe the caller prints it?

Currently the callback gets a const value (so it cannot modify it) and an int telling if the values is committed
(aka, assigned to a vatiable) or not (which then causes apl to print it). Maybe think of apl_exec("FOO") to be
essentially  ⍎"FOO" so that any printouts produced by FOO would be apl output. Not sure, though.

As far as (lib-)apl is concerned the callback decides if the result of ⍎"FOO"  will be printed.
All the magic happens at StateIndicator.cc line 542 ff.

Best Regards,
Jürgen

On 7/25/22 4:49 PM, Chris Moller wrote:

Sorry, but I have no idea how the interface between freepascal and C libraries works.  If your ⎕io is set to 1, the default, there's certainly no obvious reason for an ASCII 0 to be emitted to stdout.  Does freepascal start foreign code in a separate process?  Without reopening stdout?

On 7/24/22 17:49, enztec@gmx.com wrote:

Hi

i can see you code is c++

I am working with libapl with fpc (freepascal) and i can capture stdout and stderr fine in fpc coding
but the only stdout i get from ap_exec is the 0

i have apl_exec as a function and tried with either of the following definitions

function apl_exec(p : pchar) : longint; cdecl; // gives good results displayed but stdout captures only 0

function apl_exec(p : pchar) : ansistring; cdecl; // gives nothing to screen with apl_exec nor any stdout





On Sun, 24 Jul 2022 17:16:10 -0400

Chris Moller <moller@mollerware.com> wrote:

apl_exec() can output to both stdout and stderr.

I use:


std::stringstream outbuffer;
      std::streambuf *coutbuf = std::cout.rdbuf();
      std::cout.rdbuf(outbuffer.rdbuf());
      std::stringstream errbuffer;
      std::streambuf *cerrbuf = std::cerr.rdbuf();
      std::cerr.rdbuf(errbuffer.rdbuf());
      execerr = apl_exec (cmd.toStdString ().c_str ());
      std::cout.rdbuf(coutbuf);
      std::cerr.rdbuf(cerrbuf);
      outString = QString (outbuffer.str ().c_str ());
      errString = QString (errbuffer.str ().c_str ());

On 7/24/22 16:12, enztec@gmx.com wrote:

hello

What does libapl output?- the apl_exec function returns 0 to stdout but what is the actual display?

for example  apl_exec('⍳20')  what/where is the 1 to 20 displayed so it can be captured?

thanks

OpenPGP_0xDA6C01938888083E.asc
Description: OpenPGP public key

OpenPGP_signature
Description: OpenPGP digital signature