WARNING:

The files TRACER and WHY indicate what can be done with two programs
provided in the plog/lib directory, namely tracer.pl and ct.pl, designed
by Chris Mellish.

They provide an experimental transformation of the Prolog system and the
editor VED, which are used for teaching beginners Prolog at Sussex
University, and are included with POPLOG for anyone sophisticated enough
to make use of them.

They are designed to work with Visual-200 VDUs and VT100 VDUS, making use
of the line drawing graphics symbols on these terminals. In principle,
with the help of POP-11's LIB GRAPHCHARSETUP, can be made to work with
other VDUS.

Since they are large programs and take a long time to compile, a command
file is supplied for creating a saved image, called 'ct.psv', which may be
invoked by typing
    prolog -ct

(or possibly by the command 'ct' on its own if your system manager has set
things up appropriately.) The file is in the src directory, and may be
read (on Unix systems) with the VED command

    src remkct

(on VMS: src remkct.com)

However, the programs are supplied 'as is' and are NOT supported in their
present versions, and neither Sussex University nor Systems Designers Ltd
can offer any assistance to those who attempt to use them. Moreover, they
may change in future releases.

Aaron Sloman
August 1984
