How do I make a variable empty in Prolog?

Question

I want to empty a used variable in Prolog. For example, I want to do like this:

i = null;

but in Prolog.

How do I do this?

Answer 1

You cannot do that with pure prolog variables; once a variable is instantiated its value cannot change.

You could use global variables, but I strongly recommend to try to think a less imperative way to write the program.

edit: check DaveEdelstein's comment too