PLDB is now part of core.logic!

I highly recommend you use the version of pldb in core.logic instead of this library!

pldb

A persistent core.logic database. The goal of pldb is to provide core.logic fact/relation mechanism that doesn't use mutable namespace references. This makes it easier to use core.logic in multi-threaded environments like web applications.

Usage

Relations are defined in the same way as core.logic relations. These relations are bound to the namespace they are defined in, as in core.logic.

(pldb/db-rel man p)
(pldb/db-rel woman p)
(pldb/db-rel likes p1 p2)
(pldb/db-rel fun p)

Facts are persistent values. They can be created into a new empty db.

(def facts
  (pldb/db
   [man 'Bob]
   [man 'John]
   [man 'Ricky]

   [woman 'Mary]
   [woman 'Martha]
   [woman 'Lucy]

   [likes 'Bob 'Mary]
   [likes 'John 'Martha]
   [likes 'Ricky 'Lucy]))

Or they can extend a given base database using db-fact.

(def facts
  (-> pldb/empty-db
     (pldb/db-fact man 'Bob)
     (pldb/db-fact man 'John)
     (pldb/db-fact man 'Ricky)

     (pldb/db-fact woman 'Mary)
     (pldb/db-fact woman 'Martha)
     (pldb/db-fact woman 'Lucy)

     (pldb/db-fact likes 'Bob 'Mary)
     (pldb/db-fact likes 'John 'Martha)
     (pldb/db-fact likes 'Ricky 'Lucy)))

To retract a fact, create a new database with the fact retracted.

(def facts-retracted
  (-> facts
      (pldb/db-retraction likes 'Bob 'Mary))

To run a query with a given database, use with-db.

(pldb/with-db facts
    (doall 
      (run* [q]
        (fresh [x y]
            (likes x y)
            (fun y)
            (== q [x y])))))

To run a query across multiple databases, use with-dbs.

(pldb/with-dbs [facts1 facts2 facts3]
  (doall
    (run* [q]
        (fresh [x y]
            (likes x y)
            (fun y)
            (== q [x y])))))

Build Status

License

Copyright © 2013 ThreatGRID Inc.

Distributed under the Eclipse Public License, the same as Clojure.