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[LOGIC-52] Bug in finite domains (+fd, infd) Created: 10/Sep/12  Updated: 28/Jul/13  Resolved: 26/Oct/12

Status: Closed
Project: core.logic
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Major
Reporter: naeg Assignee: David Nolen
Resolution: Completed Votes: 1
Labels: +fd, bug, finite-domains, infd
Environment:

Clojure 1.4, core.logic 0.8-alpha3



 Description   

When running the code:

(run* [q]
(fresh [a b c d]
(infd a b c d (domain 1 3 4 5))
(+fd b 1 a)
(+fd c 1 b)
(+fd d 1 c)
(== q [a b c d])))

I get the ouput:

([5 4 3 1])

But I would expect:

()

Because [5 4 3 1] is no sequence where the next element is always one number higher than the one before.

It seems to me like +fd behaves as it would take the next element in the domain, instead of taking the next higher number (I hope I didn't misunderstand +fd or infd).



 Comments   
Comment by naeg [ 11/Sep/12 4:48 PM ]

There is workaround using membero:

(run* [q]
  (fresh [a b c d]
    (everyg #(membero % [1 3 4 5]) [a b c d])
    (+fd b 1 a)
    (+fd c 1 b)
    (+fd d 1 c)
    (== q [a b c d])))

=> ()

Note that this is quite a lot slower than it would be with infd.

Comment by David Nolen [ 26/Oct/12 1:03 AM ]

This is fixed try the latest 0.8.0 beta





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