lib/vsm: make documents kind customizable

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --git a/lib/vsm/vsm.nit b/lib/vsm/vsm.nit
index 4a64f99..d589e89 100644 (file)
--- a/lib/vsm/vsm.nit
+++ b/lib/vsm/vsm.nit
@@ -112,10 +112,13 @@ end
 # Documents can then be matched to query vectors.
 class VSMIndex
 
-       # Documents index
+       # Kind of documents stored in this index
        #
-       # TODO use a more efficient representation.
-       var documents = new HashSet[Document]
+       # Clients can redefine this type to specialize the index.
+       type DOC: Document
+
+       # Documents index
+       var documents = new HashSet[DOC]
 
        # Count for all terms in all indexed documents
        #
@@ -137,12 +140,12 @@ class VSMIndex
        #
        # Returns an `IndexMatch` for each indexed document.
        # Results are ordered by descending similarity.
-       fun match_vector(query: Vector): Array[IndexMatch] do
-               var matches = new Array[IndexMatch]
+       fun match_vector(query: Vector): Array[IndexMatch[DOC]] do
+               var matches = new Array[IndexMatch[DOC]]
                for doc in documents do
                        var sim = query.cosine_similarity(doc.tfidf)
                        if sim == 0.0 then continue
-                       matches.add new IndexMatch(doc, sim)
+                       matches.add new IndexMatch[DOC](doc, sim)
                end
                sorter.sort(matches)
                return matches
@@ -156,7 +159,7 @@ class VSMIndex
        #
        # When processing batch documents, use `auto_update = false` to disable
        # the auto update of the index.
-       fun index_document(doc: Document, auto_update: nullable Bool) do
+       fun index_document(doc: DOC, auto_update: nullable Bool) do
                for term, count in doc.terms_count do
                        if not terms_doc_count.has_key(term) then
                                terms_doc_count[term] = 1.0
@@ -196,7 +199,7 @@ class StringIndex
        # Return the Document created.
        #
        # See `index_document`.
-       fun index_string(title, uri, string: String, auto_update: nullable Bool): Document do
+       fun index_string(title, uri, string: String, auto_update: nullable Bool): DOC do
                var vector = parse_string(string)
                var doc = new Document(title, uri, vector)
                index_document(doc, auto_update)
@@ -206,7 +209,7 @@ class StringIndex
        # Match the `query` string against all indexed documents
        #
        # See `match_vector`.
-       fun match_string(query: String): Array[IndexMatch] do
+       fun match_string(query: String): Array[IndexMatch[DOC]] do
                var vector = parse_string(query)
                var doc = new Document("", "", vector)
                return match_vector(doc.terms_frequency)
@@ -241,7 +244,7 @@ class FileIndex
        # Return the created document or null if `path` is not accepted by `accept_file`.
        #
        # See `index_document`.
-       fun index_file(path: String, auto_update: nullable Bool): nullable Document do
+       fun index_file(path: String, auto_update: nullable Bool): nullable DOC do
                if not accept_file(path) then return null
                var vector = parse_file(path)
                var doc = new Document(path, path, vector)
@@ -353,11 +356,11 @@ class Document
 end
 
 # A match to a `request` in an `Index`
-class IndexMatch
+class IndexMatch[DOC: Document]
        super Comparable
 
        # Document matching the `request_vector`
-       var document: Document
+       var document: DOC
 
        # Similarity between the `request` and the `doc`.
        #
@@ -372,7 +375,7 @@ end
 class IndexMatchSorter
        super DefaultComparator
 
-       redef type COMPARED: IndexMatch
+       redef type COMPARED: IndexMatch[Document]
 
        redef fun compare(a, b) do
                return b.similarity <=> a.similarity