How do I turn off SWI-Prolog flags?

Question

I'm not sure if flags is the appropriate term, but is there anyway to configure a swi-prolog program to not output true or false on the completion of a query, and instead simply print out another statement determined in the program?

Chimera

Answer 1

There is a facility for customising this kind of behaviour, but it can get quite involved. I have not played with it myself but looking at the manual and Prolog boot files might help you.

Prolog has a "top level", which is a bit of Prolog code that controls the Prolog command line and executes the goals entered on it. With SWI-Prolog, you can specify an alternative top level:

pl -t my_quiet_prolog

If you define my_quiet_prolog/0 in a file loaded on startup, e.g. in your ~/.plrc file.

The default top level is called prolog/0. The source for this, and other parts of the default Prolog environment can be found in /usr/lib/pl-5.6.36/boot (on my Cygwin system; possibly different for you). Look at toplevel.pl for the default top level. The messages 'Yes' and 'No' are also defined, in messages.pl.

You could try to override the messages, or simply copy the top level and modify it to suite you.

Comptometer