fix issues according to pr comments

gtsam/linear/VectorValues.cpp

@@ -129,30 +129,22 @@ namespace gtsam {
   }
 
   /* ************************************************************************* */
-  bool compare(std::pair<Key, Vector>& lhs, std::pair<Key, Vector>& rhs) {
-    return lhs.first < rhs.first;
-  }
-
-  ostream& operator<<(ostream& ss, const VectorValues& v) {
-    ss << "VectorValues: "
+  ostream& operator<<(ostream& os, const VectorValues& v) {
+    os << "VectorValues"
        << ": " << 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(v.size());
+    map<Key, Vector> sorted;
     for (const auto& key_value : v) {
-      vec.push_back(std::make_pair(key_value.first, key_value.second));
+      sorted.insert(std::make_pair(key_value.first, key_value.second));
     }
-    sort(vec.begin(), vec.end(), compare);
-    for (const auto& key_value : vec)
-      ss << "  " << key_value.first << ": " << key_value.second.transpose()
-         << "\n";
+    for (const auto& key_value : sorted)
 #else
     for (const auto& key_value : v)
-      ss << "  " << key_value.first << ": " << key_value.second.transpose()
-         << "\n";
 #endif
-    return ss;
+      os << "  " << key_value.first << ": " << key_value.second.transpose()
+         << "\n";
+    return os;
   }
 
   /* ************************************************************************* */

gtsam/linear/VectorValues.h

@@ -29,7 +29,7 @@
 
 #include <map>
 #include <string>
-#include <iostream>
+#include <iosfwd>
 
 namespace gtsam {
 
@@ -229,13 +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);
+    /// overload operator << to print to stringstream
+    friend std::ostream& operator<<(std::ostream&, const VectorValues&);
 
     /** print required by Testable for unit testing */
-    void print(const std::string& str = "VectorValues: ",
+    void print(const std::string& str = "VectorValues",
         const KeyFormatter& formatter = DefaultKeyFormatter) const;
 
     /** equals required by Testable for unit testing */

gtsam/linear/tests/testVectorValues.cpp

@@ -241,10 +241,9 @@ TEST(VectorValues, print)
   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";
+      "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());
 }