Changeset 3466

Timestamp:

Feb 10, 2016, 4:39:38 AM (6 years ago)

Author:

Peter

Message:

closes #842. Document how to combine compose_f_gx_hy, PairFirst?, and std::less to accomplish a functor that compares pairs ignore .second. Also include such an example in the test.

Location:

trunk

Files:

• test/utility.cc (modified) (3 diffs)
• yat/utility/stl_utility.h (modified) (1 diff)

trunk/test/utility.cc

@@ -78 +78 @@
 void test_compose_functors(test::Suite& suite);
 void test_dereferencer(test::Suite& suite);
+void test_ticket842(test::Suite& suite);
 
 int main(int argc, char* argv[])
@@ -230 +231 @@
   test_rename(suite);
   test_replace(suite);
+  test_ticket842(suite);
 
   return suite.return_value();
@@ -757 +759 @@
     suite.err() << "error: " << s << "\n";
 }
+
+
+void test_ticket842(test::Suite& suite)
+{
+  suite.out() << "test_ticket842\n";
+  std::vector<std::pair<std::string, int> > data;
+  data.push_back(std::make_pair("Orange", 2));
+  data.push_back(std::make_pair("Orange", 1));
+  data.push_back(std::make_pair("Apple", 10));
+
+  typedef utility::PairFirst<const std::pair<std::string, int> > PF;
+  typedef std::less<std::string> strLess;
+  utility::compose_f_gx_hy<strLess, PF, PF> compare;
+  // stable sort should shuffle 'Apple' first, and then keep the order
+  // of the equaivalent 'Orange' elements, i.e., <Orange, 2> should stay
+  // before <Orange, 1>.
+  std::stable_sort(data.begin(), data.end(), compare);
+  if (!suite.add(data[0].first == "Apple"))
+    suite.err() << "incorrect data[0].first: " << data[0].first << "\n";
+  if (!suite.add(data[1].first == "Orange"))
+    suite.err() << "incorrect data[1].first: " << data[1].first << "\n";
+  if (!suite.add(data[1].second == 2))
+    suite.err() << "incorrect data[1].second: " << data[1].second << "\n";
+}

trunk/yat/utility/stl_utility.h

@@ -160 +160 @@
 
      \see compose_f_gxy, compose_f_gx, and compose_f_gx_hx
+
+     Here is an example using the class to construct a functor that
+     compares std::pairs ignoring \c second.
+
+     \code
+     vector<pair<string, foo> > data;
+     data.push_back(make_pair("Orange", foo(2));
+     data.push_back(make_pair("Orange", foo(1));
+     data.push_back(make_pair("Apple", foo(10));
+     typedef PairFirst<const pair<string, foo> > PF;
+     compose_f_gx_hy<less<string>, PF, PF> compare;
+     sort(data.begin(), data.end(), compare);
+     \endcode
+
    */
   template<class F, class G, class H>