MiniKanren fresh

fresh (x...) g ...

Binds fresh variables to x ... and succeeds if the goals g ... succeed.

Q: When is a variable fresh? A: When it has no association.


Both q, x are fresh variables at first

(run* (q)
  (fresh (x)
    (== #t x)
    (== #t q)))

Law of fresh

If x is fresh, (v x) succeeds and associates x with v.

(v w) is the same as (w v). (association of fresh variables is commutative)

Reification of a fresh variable.

Where x is fresh:

x == (_.0)

Created with (reify-name 0)