miniKanren (logpy, or others) how to assert a fact is true?

Question

I am doing an exercise to write some logic code in a few different idioms... Prolog, miniKanren, ASP etc... to get a feel for each.

I have a question about something really basic:

In Prolog you can define:

human(bob).

then in the REPL you can check the truth of this fact and a non-fact:

?- human(bob).
true.

?- human(e_t).
false.

In the python miniKanren, LogPy, you can similarly define the fact:

from kanren import fact

fact(human, 'bob')

I cannot find a recipe for simply checking the truth of "bob is human".

The run function seems to require a variable as the second arg, but I am an not trying to find the value of a variable.

All the kanren examples I found start by showing how to query a relation, like:

from kanren import Relation, fact, run, var

human = Relation()

fact(human, 'bob')
fact(human, 'jim')

x = var('x')

run(0, x, human(x))

# output:
('jim', 'bob')

That's more useful, but what I want to do is even simpler than that (just for the sake of comparing the same baby steps in Prolog).

Answer 1

So... while writing out this question I played around a bit more and found a recipe for what I'm trying to do.

This works in the LogPy miniKanren, I would love to know if a similar usage is applicable in other implementations such as Clojure core.logic etc (or if there's another way to do it!).

from kanren import Relation, fact, run, var

human = Relation()

fact(human, 'bob')

run(0, True, human('bob'))
>>> (True,)

run(0, True, human('E.T.'))
>>> ()

We can use anything in place of the True arg: if the goal arg evaluates true then you will get your value back in the result tuple, otherwise an empty result.