Question

I am new to Prolog and am experimenting around with some stuff, in particular i’m thinking about how to do a certain thing in prolog. I am aware of facts and rules, facts being something of the sort

specialCustomer(x).                     //person x is a specialcustomer

and rules:

totalSpend(x,500) :- specialCustomer(x).     //if x spends 500, he is a special customer

Would this fact and rule be valid in prolog? Is the rule wrong? How would i be able to query this through prolog? As in would a call of

totalSpend(bob,500).

be a valid call?

sorry if i am answering my own question, i just seem to be a bit…well confused!

Answer 1

If you want to say that Bob, Jim and everyone who spends more than 500 are special customers, then define some people’s spending, you would define it as follows:

specialCustomer(bob).
specialCustomer(jim).
specialCustomer(Who) :-
  totalSpend(Who, Amount),
  Amount >= 500.

totalSpend(mary, 400).
totalSpend(jack, 600).
totalSpend(pam, 500).

Then you would query it as follows:

?- specialCustomer(jim).
true.

?- specialCustomer(mary).
false.

?- specialCustomer(jack).
true.

?- specialCustomer(pam).
true.

?- specialCustomer(X).
X = bob ;
X = jim ;
X = jack ;
X = pam.