Allow tying multiple noms in one binder

Question

I think it may be useful to be able to tie multiple noms in one binder, with or without significant order.

A couple use cases I've thought of so far:

Lambdas in a non-currying language. Here order matters.

(== (list 'fn (ties [x y] (list '+ x y)))
    (list 'fn (ties [z w] (list '+ z w)))


My original use case, free/quantified variables in logical formulas. Order doesn't matter (note the second body has its noms swapped).

(== (list '∀ (ties #{x y} (list '= (list '+ x y) (list '+ y x))))
    (list '∀ (ties #{z w} (list '= (list '+ w z) (list '+ z w)))))



I have a draft implementation here: https://github.com/tomjack/core.logic/compare/ties

Possible issues with this implementation:
- Is it OK to reextend IWalkTerm to IPersistentSet?
- Should Tie and Ties present a uniform interface? (e.g. (tie? (ties #{x} x)))

Answer 1

Comment made by: dnolen

I really don't think the set bit is necessary, the vector syntax is fine. Also avoid needing to bring IWalkTerm back for sets. And yes, tie? should work in either case.

Answer 2

Comment made by: tomoj

Hmm.. should:

`
(== (list 'fn (ties [x y] (list '- x y)))

(list 'fn (ties [z w] (list '- w z)))

`

I'd think not.

Do you mean that order should always matter (take out the permutations stuff), or that it should never matter (don't use ties for cases like the above)?

Answer 3

Comment made by: dnolen

Ah hm, good point. Will think on it some more.

Answer 4

Reference: https://clojure.atlassian.net/browse/LOGIC-138 (reported by tomoj)