[eclipse-users] Simple question on example in Tutorial

Hi folks,

 

I'm looking at the example for "Call" (Section 3.7.3 of "A Tutorial
Introduction",

v 21 Apr 2007) and I'm missing the point about how this defines
disjunction:

 

X ; Y :- call(X).

X ; Y :- call(Y).

 

Each of these disjunction clauses seems to be formed by two other
clauses,

one just being "X" and the other being the implication of Y by either a
call(X)

or call(Y).

 

Or is it that the entire "left side" ("X ; Y", for example) is implied
by the right

side? As I am fairly new to ECLiPSe / Prolog, something of the syntax
here

escapes me. Any further explanation would be greatly appreciated.  From
a

different text I thought I recalled that Prolog "Head :- Body" clauses
are Horn

clauses, so there should only be one structure in the Head, but I could
be

wrong.

 

Thanks!

 

Chuck Lutz

Lockheed Martin

Systems of Systems Engineering

BMC4I Modeling and Simulation

Moorestown, NJ

(856)638-7234 (office)

charles.d.lutz_at_lmco.com

 

"A graphic is never an end in itself; it is a moment

in the process of decision making."
     - Jacques Bertin