How to get the next solution of a SWI-prolog query with QProcess?

Question

I'm trying to combine SWI-prolog with QProcess. So I already can interact with prolog and send questions to it, but I always getting only the first answer. So I tried to send such characters like "n" or "r" which should give me the next answer of my query like in the shell. However, it doesn't work with QProcess. Here is my code:

connect(&p,SIGNAL(readyReadStandardError()),this,SLOT(readStdError()));
connect(&p,SIGNAL(readyReadStandardOutput()),this,SLOT(readStdOut()));

p.setProcessChannelMode(QProcess::MergedChannels);
p.start("swipl",QIODevice::ReadWrite | QIODevice::Unbuffered);
if(!p.waitForStarted())
    return;

p.write("consult(ws).\r\n");      //prolog program
if(!p.waitForBytesWritten())
{
    p.close();
    return;
}

p.write("test(X,Y).\r\n");       //query
if(!p.waitForBytesWritten())
{
    p.close();
    return;
}

p.write("n",1);                  //give me the next solution -> nothing happens

I don't know what to do anymore. How can I get the next answers or how can I tell prolog to show me all answers?

I remember, SWI-Prolog had an API interface for embedding into apps... — hate-engine, Dec 24 '12 at 13:17
Yes, embedding in Qt it's a concrete possibility I'm actually working on... — CapelliC, Dec 24 '12 at 17:22

score 1 · Accepted Answer · answered Dec 24 '12 at 11:43

I would use something like

p.write("forall(test(X,Y), writeln(test(X,Y))).\r\n");

or something a bit more reusable

QString q("forall(%1, writeln(%1)).\r\n");
p.write(q.arg("test(X,Y)"));

you got the concept...

If you prefer, maybe to ease answer parsing, print separed variables

p.write("forall(test(X,Y), maplist(writeln, [X,Y])).\r\n");

How to get the next solution of a SWI-prolog query with QProcess?

1 Answers1