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operators in symbolics prolog
having some difficulties with symbolics prolog. any hints on the foolowing?
/**********************************************************************
freely yanked from:
Bratko, Ivan. _PROLOG Programming for Artificial Intelligence._
Addison-Wesley, 1986.
**********************************************************************/
% p. 82
:- op(800, xfx, <===>).
:- op(700, xfy, v).
:- op(600, xfy, &).
:- op(500, fy, ~).
% ~(A & B) <===> ~A v ~B.
traps with a warning about changing a read-table binding, then says that
the predicate (:prolog-predicate <===> 2) is undefined.
---
running rel 6.1 on a 3670.
ad...THANKS...vance!
john c akbari
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