Added new iterator and tests

ptrie/iterator_test.go

@@ -0,0 +1,28 @@
+package ptrie
+
+import "testing"
+
+func TestIterator(t *testing.T) {
+	trie := NewEmpty()
+	vals := []struct{ k, v string }{
+		{"do", "verb"},
+		{"ether", "wookiedoo"},
+		{"horse", "stallion"},
+	}
+	v := make(map[string]bool)
+	for _, val := range vals {
+		v[val.k] = false
+		trie.UpdateString(val.k, val.v)
+	}
+
+	it := trie.Iterator()
+	for it.Next() {
+		v[string(it.Key)] = true
+	}
+
+	for k, found := range v {
+		if !found {
+			t.Error("iterator didn't find", k)
+		}
+	}
+}