add capacity interface

flat_map.hpp

@@ -110,6 +110,18 @@ namespace flat_hpp
         const_reverse_iterator rend() const noexcept { return data_.rend(); }
         const_reverse_iterator crend() const noexcept { return data_.crend(); }
 
+        bool empty() const noexcept {
+            return data_.empty();
+        }
+
+        size_type size() const noexcept {
+            return data_.size();
+        }
+
+        size_type max_size() const noexcept {
+            return data_.max_size();
+        }
+
         template < typename P
                  , typename = std::enable_if_t<std::is_constructible<value_type, P>::value> >
         std::pair<iterator, bool> insert(P&& p) {

flat_map_tests.cpp

@@ -96,6 +96,13 @@ TEST_CASE("flat_map") {
             auto s3 = map_t({{0,1}, {1,2}}, std::less<int>(), alloc_t());
         }
     }
+    SECTION("capacity") {
+        using map_t = flat_map<int, unsigned>;
+        map_t s0;
+        s0.empty();
+        s0.size();
+        s0.max_size();
+    }
     SECTION("inserts") {
         struct obj_t {
             obj_t(int i) : i(i) {}

flat_set.hpp

@@ -109,6 +109,18 @@ namespace flat_hpp
         const_reverse_iterator rend() const noexcept { return data_.rend(); }
         const_reverse_iterator crend() const noexcept { return data_.crend(); }
 
+        bool empty() const noexcept {
+            return data_.empty();
+        }
+
+        size_type size() const noexcept {
+            return data_.size();
+        }
+
+        size_type max_size() const noexcept {
+            return data_.max_size();
+        }
+
         template < typename P
                  , typename = std::enable_if_t<std::is_constructible<value_type, P>::value> >
         std::pair<iterator, bool> insert(P&& p) {

flat_set_tests.cpp

@@ -87,6 +87,13 @@ TEST_CASE("flat_set") {
             auto s3 = set_t({0,1,2}, std::less<int>(), alloc_t());
         }
     }
+    SECTION("capacity") {
+        using set_t = flat_set<int>;
+        set_t s0;
+        s0.empty();
+        s0.size();
+        s0.max_size();
+    }
     SECTION("inserts") {
         struct obj_t {
             obj_t(int i) : i(i) {}