overload operator <<, and add unittest

gtsam/linear/VectorValues.cpp

@@ -133,25 +133,32 @@ bool compare(std::pair<Key, Vector>& lhs, std::pair<Key, Vector>& rhs) {
     return lhs.first < rhs.first;
   }
 
-void VectorValues::print(const string& str,
+  ostream& operator<<(ostream& ss, const VectorValues& v) {
-                         const KeyFormatter& formatter) const {
+    ss << "VectorValues: "
-  cout << str << ": " << size() << " elements\n";
+       << ": " << v.size() << " elements\n";
     // Change print depending on whether we are using TBB
 #ifdef GTSAM_USE_TBB
     std::vector<std::pair<Key, Vector>> vec;
-  vec.reserve(size());
+    vec.reserve(v.size());
-  for (const value_type& key_value : *this) {
+    for (const auto& key_value : v) {
       vec.push_back(std::make_pair(key_value.first, key_value.second));
     }
     sort(vec.begin(), vec.end(), compare);
     for (const auto& key_value : vec)
-    cout << "  " << formatter(key_value.first) << ": "
+      ss << "  " << key_value.first << ": " << key_value.second.transpose()
-         << key_value.second.transpose() << "\n";
+         << "\n";
 #else
-  for (const value_type& key_value : *this)
+    for (const auto& key_value : v)
-    cout << "  " << formatter(key_value.first) << ": "
+      ss << "  " << key_value.first << ": " << key_value.second.transpose()
-         << key_value.second.transpose() << "\n";
+         << "\n";
 #endif
+    return ss;
+  }
+
+  /* ************************************************************************* */
+  void VectorValues::print(const string& str,
+                           const KeyFormatter& formatter) const {
+    cout << *this;
     cout.flush();
 }
 

gtsam/linear/VectorValues.h

@@ -29,6 +29,7 @@
 
 #include <map>
 #include <string>
+#include <iostream>
 
 namespace gtsam {
 
@@ -228,6 +229,11 @@ namespace gtsam {
      */
     const_iterator find(Key j) const { return values_.find(j); }
 
+    /**
+     * overload operator << to print to stringstream
+     */
+    friend std::ostream& operator<<(std::ostream& ss, const VectorValues& v);
+
     /** print required by Testable for unit testing */
     void print(const std::string& str = "VectorValues: ",
         const KeyFormatter& formatter = DefaultKeyFormatter) const;

gtsam/linear/tests/testVectorValues.cpp

@@ -24,6 +24,8 @@
 #include <boost/assign/list_of.hpp>
 #include <boost/range/adaptor/map.hpp>
 
+#include <sstream>
+
 using namespace std;
 using namespace boost::assign;
 using boost::adaptors::map_keys;
@@ -228,6 +230,24 @@ TEST(VectorValues, vector_sub)
   EXPECT(assert_equal(expected, vv.vector(dims)));
 }
 
+/* ************************************************************************* */
+TEST(VectorValues, print)
+{
+  VectorValues vv;
+  vv.insert(0, (Vector(1) << 1).finished());
+  vv.insert(1, Vector2(2, 3));
+  vv.insert(2, Vector2(4, 5));
+  vv.insert(5, Vector2(6, 7));
+  vv.insert(7, Vector2(8, 9));
+
+  string expected =
+      "VectorValues: : 5 elements\n  0: 1\n  1: 2 3\n  2: 4 5\n  5: 6 7\n  7: 8 9\n";
+  stringstream actual;
+  actual << vv;
+
+  EXPECT(expected == actual.str());
+}
+
 /* ************************************************************************* */
 int main() { TestResult tr; return TestRegistry::runAllTests(tr); }
 /* ************************************************************************* */