diff options
Diffstat (limited to 'src/clojure/contrib/datalog/database.clj')
| -rw-r--r-- | src/clojure/contrib/datalog/database.clj | 38 |
1 files changed, 33 insertions, 5 deletions
diff --git a/src/clojure/contrib/datalog/database.clj b/src/clojure/contrib/datalog/database.clj index 8fef6524..517c1b92 100644 --- a/src/clojure/contrib/datalog/database.clj +++ b/src/clojure/contrib/datalog/database.clj @@ -145,14 +145,25 @@ [db] (map-values #(-> % :data count) db)) -(defn- add-to-indexes - "Adds the tuple to the appropriate keys in the index map" - [idxs tuple] +(defn- modify-indexes + "Perform f on the indexed tuple-set. f should take a set and tuple, + and return the new set." + [idxs tuple f] (into {} (for [ik (keys idxs)] (let [im (idxs ik) iv (tuple ik) os (get im iv #{})] - [ik (assoc im iv (conj os tuple))])))) + [ik (assoc im iv (f os tuple))])))) + +(defn- add-to-indexes + "Adds the tuple to the appropriate keys in the index map" + [idxs tuple] + (modify-indexes idxs tuple conj)) + +(defn- remove-from-indexes + "Removes the tuple from the appropriate keys in the index map" + [idxs tuple] + (modify-indexes idxs tuple disj)) (defn add-tuple "Two forms: @@ -170,8 +181,25 @@ (if (identical? data new-data) ; optimization hack! rel (let [idxs (add-to-indexes (:indexes rel) tuple)] - (assoc rel :data (conj (:data rel) tuple) :indexes idxs)))))) + (assoc rel :data new-data :indexes idxs)))))) + +(defn remove-tuple + "Two forms: + + [db relation-name tuple] removes the tuple from the named relation, + returns a new database. + [rel tuple] removes the tuple from the relation. Returns the new + relation." + ([db rel-name tuple] (assoc db rel-name (remove-tuple (db rel-name) tuple))) + ([rel tuple] + (let [data (:data rel) + new-data (disj data tuple)] + (if (identical? data new-data) + rel + (let [idxs (remove-from-indexes (:indexes rel) tuple)] + (assoc rel :data new-data :indexes idxs)))))) + (defn add-tuples "Adds a collection of tuples to the db, as (add-tuples db |