🚀 go-pugleaf

    Last night, in PDC prolog I was trying to write the following predicate:

         gofirst(Player) :-
             random(RandNum),
             RandNum < 0.5, Player = computer ;
             RandNum >= 0.5, Player = opponent.

    When I tried to run the program, I got the message 'Free variables
not allowed here', at Player = opponent.
    Is this a quirk of PDC prolog, or don't I fully understand disjunction?

                                                         [Tim]