added pull to open-addressing containers (#309)

* added pull to open-addressing containers

* added pull_tests.cpp

* guarded pull against exceptions in mid init_type construction

test/unordered/pull_tests.cpp

@@ -0,0 +1,88 @@
+// Copyright 2025 Joaquin M Lopez Munoz.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+#include "../helpers/test.hpp"
+#include "../helpers/unordered.hpp"
+#include <algorithm>
+#include <vector>
+
+struct move_only_type
+{
+  move_only_type(int n_): n{n_} {}
+  move_only_type(move_only_type&&) = default;
+  move_only_type(const move_only_type&) = delete;
+
+  move_only_type& operator=(move_only_type&&) = default;
+
+  int n;
+};
+
+bool operator==(const move_only_type& x, const move_only_type& y)
+{
+  return x.n == y.n;
+}
+
+bool operator<(const move_only_type& x, const move_only_type& y)
+{
+  return x.n < y.n;
+}
+
+std::size_t hash_value(const move_only_type& x)
+{
+  return boost::hash<int>()(x.n);
+}
+
+template<typename T>
+struct from_int
+{
+  T operator()(int n) const { return T(n); }
+};
+
+template<typename T, typename U>
+struct from_int<std::pair<T, U> >
+{
+  std::pair<T, U> operator()(int n) const { return {n, -n}; }
+};
+
+template <class Container> void test_pull()
+{
+  Container c;
+  using init_type = typename Container::init_type;
+
+  std::vector<init_type> l1;
+  from_int<init_type> fi;
+  for(int i = 0; i < 1000; ++i ){
+    l1.push_back(fi(i));
+    c.insert(fi(i));
+  }
+
+  std::vector<init_type> l2;
+  for(auto first = c.cbegin(), last = c.cend(); first != last; )
+  {
+    l2.push_back(c.pull(first++));
+  }
+  BOOST_TEST(c.empty());
+
+  std::sort(l1.begin(), l1.end());
+  std::sort(l2.begin(), l2.end());
+  BOOST_TEST(l1 == l2);
+}
+
+UNORDERED_AUTO_TEST (pull_) {
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+  test_pull<
+    boost::unordered_flat_map<move_only_type, move_only_type> >();
+  test_pull<
+    boost::unordered_flat_set<move_only_type> >();
+  test_pull<
+    boost::unordered_node_map<move_only_type, move_only_type> >();
+  test_pull<
+    boost::unordered_node_set<move_only_type> >();
+#else
+  // Closed-addressing containers do not provide pull
+#endif
+}
+
+RUN_TESTS()