Interesting. Is Byrd's dissertation available online? On Dec 4, 9:41 pm, David Nolen <dnolen.li...@gmail.com> wrote: > I announced it earlier this week on Twitter, but it's now come far along > enough to be usable. You can write fun stuff like the following: > > (defn likes > [x y] > (cond-e > ((== x 'john) (== y 'mary)) > ((== x 'mary) (== y 'john)))) > > (defn musician [x] > (cond-e > ((== x 'john)) > ((== x 'bob)))) > > (run* [q] > (likes q 'mary) > (musician q)) > ;; [john] > > (run* [q] > (musician q)) > ;; [john bob] > > (run* [q] > (exist [x y] > (likes x y) > (== [x y] q))) > ;; [[john mary] [mary john]] > > My inspiration to start on this was Jim Duey's implementation. However I had > two specific goals - > > * Focus on performance. While developing I compared performance against > miniKanren under Racket - I made sure the Clojure implementation ran at > least as fast, and in many cases it runs quite a bit faster > * Implement "growable" sequences without resorting to Scheme's dotted pairs. > This required me to develop a new protocol in which iteration might return a > logic var instead of nil or a Seq. > > The implementation started with the one described William Byrd's > dissertation. However a considerable number of changes were made- > > * substitutions are implemented as a protocol and a defrecord > * substitutions internally use a PersistentHashMap as well as > PersistentVector (for debugging) > * supports unification of all the Clojure data structures supported by > clojure.walk > * goal and goal constructors are implements as deftypes (Mzero, Unit, > Choice, Inc) and those implement IMPlus and IBind protocols. > > The code base is compact, some ~450 lines of Clojure. > > Future directions: > * Friendlier interface for defining facts and running queries > * There are many great ideas in William Byrd's thesis that need looking > into. In particular I'm interested in tabling. > * Investigating replacing the PersistentHashMap with a Skew Binary Random > Access List or a Finger Tree. This would speed up the performance of the > most expensive functions in the system, walk. In the Scheme implementations > SBRALs can lead to 2.5X-100X in performance. > * Modifying the core macros to optimize logic programs. > * Parallel logic programming. > > Source and more info here,https://github.com/swannodette/logos.
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