Add nth(size_type index) method.

Tessil · Jul 4, 2017 · 657c9e5 · 657c9e5
1 parent 0468aca
commit 657c9e5
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diff --git a/src/ordered_map.h b/src/ordered_map.h
@@ -653,6 +653,14 @@ class ordered_hash: private Hash, private KeyEqual {
         return insert_impl(std::forward<K>(key), hash_key(key)).first.value();
     }
 
+    iterator nth(size_type index) {
+        return iterator(m_values.begin() + index);
+    }
+
+    const_iterator nth(size_type index) const {
+        return const_iterator(m_values.cbegin() + index);
+    }
+
     const_reference front() const {
         return m_values.front();
     }
@@ -1547,9 +1555,31 @@ class ordered_map {
     /*
      * Other
      */
+
+    /**
+     * Requires index <= size().
+     * 
+     * Return an iterator to the element at index. Return end() if index == size().
+     */
+    iterator nth(size_type index) { return m_ht.nth(index); }
+
+    /**
+     * @copydoc nth(size_type index)
+     */
+    const_iterator nth(size_type index) const { return m_ht.nth(index); }
+
+
+    /**
+     * Return const_reference to the first element. Requires the container to not be empty.
+     */
     const_reference front() const { return m_ht.front(); }
+
+    /**
+     * Return const_reference to the last element. Requires the container to not be empty.
+     */
     const_reference back() const { return m_ht.back(); }
 
+
     /**
      * Only available if ValueTypeContainer is a std::vector. Same as calling 'values_container().data()'.
      */
@@ -1964,9 +1994,31 @@ class ordered_set {
     /*
      * Other
      */
+
+    /**
+     * Requires index <= size().
+     * 
+     * Return an iterator to the element at index. Return end() if index == size().
+     */
+    iterator nth(size_type index) { return m_ht.nth(index); }
+
+    /**
+     * @copydoc nth(size_type index)
+     */
+    const_iterator nth(size_type index) const { return m_ht.nth(index); }
+
+
+    /**
+     * Return const_reference to the first element. Requires the container to not be empty.
+     */
     const_reference front() const { return m_ht.front(); }
+
+    /**
+     * Return const_reference to the last element. Requires the container to not be empty.
+     */
     const_reference back() const { return m_ht.back(); }
 
+
     /**
      * Only available if ValueTypeContainer is a std::vector. Same as calling 'values_container().data()'.
      */ 

diff --git a/tests/ordered_map_tests.cpp b/tests/ordered_map_tests.cpp
@@ -644,6 +644,45 @@ BOOST_AUTO_TEST_CASE(test_swap) {
     BOOST_CHECK(map2 == (tsl::ordered_map<int64_t, int64_t>{{1, 10}, {8, 80}, {3, 30}}));
 }
 
+/**
+ * front(), back()
+ */
+BOOST_AUTO_TEST_CASE(test_front_back) {
+    tsl::ordered_map<int64_t, int64_t> map = {{1, 10}, {2, 20}};
+    map.insert({0, 0});
+
+    BOOST_CHECK(map.front() == (std::pair<int64_t, int64_t>(1, 10)));
+    BOOST_CHECK(map.back() == (std::pair<int64_t, int64_t>(0, 0)));
+
+
+    map.clear();
+    map.insert({3, 30});
+    BOOST_CHECK(map.front() == (std::pair<int64_t, int64_t>(3, 30)));
+    BOOST_CHECK(map.back() == (std::pair<int64_t, int64_t>(3, 30)));
+}
+
+/**
+ * nth()
+ */
+BOOST_AUTO_TEST_CASE(test_nth) {
+    tsl::ordered_map<int64_t, int64_t> map = {{1, 10}, {2, 20}};
+    map.insert({0, 0});
+
+    BOOST_CHECK(map.nth(0) != map.end());
+    BOOST_CHECK(*map.nth(0) == (std::pair<int64_t, int64_t>(1, 10)));
+
+    BOOST_CHECK(map.nth(1) != map.end());
+    BOOST_CHECK(*map.nth(1) == (std::pair<int64_t, int64_t>(2, 20)));
+
+    BOOST_CHECK(map.nth(2) != map.end());
+    BOOST_CHECK(*map.nth(2) == (std::pair<int64_t, int64_t>(0, 0)));
+
+    BOOST_CHECK(map.nth(3) == map.end());
+
+
+    map.clear();
+    BOOST_CHECK(map.nth(0) == map.end());
+}
 
 /**
  * other