Turbo Prolog

3 Tutorial I:
Five Simple Programs
This is the first of eight chapters giving a step-by-step tutorial introduction to the Turbo
Prolog language. It begins with a study of the structure of a Turbo Prolog program, first
by means of a simple example and then by examining the fundamental components of
a program, one by one. In every case, our starting point will be a motivating example
with the threads drawn together a little more formally at the end of the chapter.
(Chapters II and 12 contain very precise definitions of all Turbo Prolog features. At this
stage in the tutorial it's getting started that matters.)
Apart from program structure, the two other important ideas introduced in this chapter
are backtracking (which is how Prolog searches for all possible solutions to a goal)
and how to make Prolog check if something is not true-at least as far as the available
information makes it possible to determine.
THE STRUCTURE OF
A TURBO PROLOG PROGRAM
Consider the following example program:
1* Program 1 *1
domains
person, activity = symbol
predicates
likes(person,activity)
clauses
likes(ellen,tennis).
likes(john,football).
likes(tom,baseball).
likes(eric,swimming).
likes(mark,tennis).
likes(bill,X) if likes(tom,X).
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