ProXL is a direct interface to the X Window System. You may want to use ProXL in your ProXT programs in order to do graphics or use some of the X Window System's more subtle features not supported directly by the X toolkit.
ProXT provides a library file, library(xif), which allows ProXL
predicates to be used smoothly in your ProXT programs. In order to
use any of these predicates, you must load library(xif). Quintus
distributes the source code for xif.pl and users are encouraged to
look at it for examples of mixed ProXL/ProXT programming.
If you need to use ProXT and ProXL together, make sure your code has:
:- use_module(library(proxt)).
:- use_module(library(proxl)).
:- use_module(library(xif)).