feat: implement ostream operator for timer

lib_vector_search/include/timer.h

@@ -15,3 +15,5 @@ public:
 
   long us() const;
 };
+
+std::ostream &operator<<(std::ostream &os, const Timer &timer);

lib_vector_search/src/timer.cpp

@@ -12,3 +12,21 @@ long Timer::us() const {
   return std::chrono::duration_cast<std::chrono::microseconds>(end_ - start_)
       .count();
 }
+
+std::ostream &operator<<(std::ostream &os, const Timer &timer) {
+  long time = timer.us();
+
+  if (time >= 1e6) {
+    os << time / static_cast<long>(1e6) << " s ";
+    time %= static_cast<long>(1e6);
+  }
+
+  if (time >= 1e3) {
+    os << time / static_cast<long>(1e3) << " ms ";
+    time %= static_cast<long>(1e3);
+  }
+
+  os << time << " µs";
+
+  return os;
+}

vector_search_cli/main.cpp

@@ -17,7 +17,7 @@ vector<string> generate_word_list() {
   auto word_list = WordListGenerator().generate();
   generator_timer.stop();
 
-  cout << "word list generator took " << generator_timer.us() << " µs" << endl;
+  cout << "word list generator took " << generator_timer << endl;
   cout << "word list is " << word_list.size() << " element(s) long" << endl;
 
   return word_list;
@@ -34,7 +34,7 @@ void test_linear_finder(const vector<string> &word_list) {
   auto result = linear_finder.find_prefix("ABCD");
   find_timer.stop();
 
-  cout << "linear finder took " << find_timer.us() << " µs" << endl;
+  cout << "linear finder took " << find_timer << endl;
   cout << "result list is " << result.size() << " element(s) long" << endl;
 }
 
@@ -53,7 +53,7 @@ void test_parallel_finder(const vector<string> &word_list) {
   auto result = parallel_finder.find_prefix("ABCD");
   find_timer.stop();
 
-  cout << "parallel finder took " << find_timer.us() << " µs" << endl;
+  cout << "parallel finder took " << find_timer << endl;
   cout << "result list is " << result.size() << " element(s) long" << endl;
 }