Complete LANGMATCHES implementation.

Author: RubenVerborgh

lib/util/SparqlExpressionEvaluator.js

@@ -135,8 +135,13 @@ operators = {
   'lang': function (a)    {
     return '"' + N3Util.getLiteralLanguage(a).toLowerCase() + '"';
   },
-  'langmatches': function (a, b) {
-    return a.toLowerCase() === b.toLowerCase();
+  'langmatches': function (langTag, langRange) {
+    // Implements https://tools.ietf.org/html/rfc4647#section-3.3.1
+    langTag = langTag.toLowerCase();
+    langRange = langRange.toLowerCase();
+    return langTag === langRange ||
+           (langRange = literalValue(langRange)) === '*' ||
+           langTag.substr(1, langRange.length + 1) === langRange + '-';
   },
   'contains': function (string, substring) {
     substring = literalValue(substring);

test/util/SparqlExpressionEvaluator-test.js

@@ -343,11 +343,20 @@ describe('SparqlExpressionEvaluator', function () {
       var evaluator = SparqlExpressionEvaluator({
         type: 'operation',
         operator: 'langmatches',
-        args: ['?l', '"EN"'],
+        args: ['"de-DE-1996"', '?l'],
       });
 
-      it('should return true if the language matches', function () {
-        evaluator({ '?l': '"en"' }).should.equal(TRUE);
+      it('should return true if the language is equal', function () {
+        evaluator({ '?l': '"de-de-1996"' }).should.equal(TRUE);
+      });
+
+      it('should return true if the language has the same prefix', function () {
+        evaluator({ '?l': '"de"' }).should.equal(TRUE);
+        evaluator({ '?l': '"de-DE"' }).should.equal(TRUE);
+      });
+
+      it('should return true on *', function () {
+        evaluator({ '?l': '"de-de-1996"' }).should.equal(TRUE);
       });
 
       it("should return false if the language doesn't match", function () {