Fix/null variant_collection (#27)

* fixed boost::variant_collection_of<>

* added tests for ==/!=

.drone.jsonnet

@@ -6,7 +6,7 @@ local library = "poly_collection";
 
 local triggers =
 {
-    branch: [ "master", "develop", "feature/*" ]
+    branch: [ "master", "develop", "feature/*", "fix/*" ]
 };
 
 local ubsan = { UBSAN: '1', UBSAN_OPTIONS: 'print_stacktrace=1' };

doc/reference.qbk

@@ -1876,7 +1876,8 @@ For the description of the algorithms we use the following notation:
 of a collection of Boost.PolyCollection such that \[`first`, `middle`) and
 \[`middle`, `last`) are valid ranges.
 * `args...` is a function parameter pack of types `Args&&...`,
-* `Ts...` is a template parameter pack of arbitrary types.
+* `Ts...` is a template parameter pack of acceptable types for the collection,
+plus optionally `all_types` in the case of closed collections.
   * Open collections: `Us...` is defined as `Ts...`.
   * Closed collections: `Us...` is defined as the set of all acceptable types
   in the collection if `all_types` is in `Ts...`, or as `Ts...` otherwise.
@@ -1917,7 +1918,7 @@ value, which disallows this type of polymorphism.].[br]
 [*Effects:] Equivalent to `expr`.[br]
 [*Returns:] `expr`.[br]
 [*Complexity:] That of `expr`.[br]
-[*Note:] In the case of closed collections, if `Us...` contains all the
+[*Note:] In the case of closed collections, if `Us...` is not empty and contains all the
 acceptable types of the collection (/total restitution/), then
 the dereference operation of `rfirst`, `rmiddle` and `rlast` to the
 collection's `value_type` is not ever instantiated.

include/boost/poly_collection/detail/type_restitution.hpp

@@ -177,8 +177,8 @@ struct restitute_range_class<std::true_type /* total */,F,T>
   F f;
 };
 
-template<typename F>
-struct restitute_range_class<std::false_type /* non total */,F>
+template<typename IsTotal,typename F>
+struct restitute_range_class<IsTotal,F>
 {
   restitute_range_class(const F& f):f(f){}
   
@@ -266,8 +266,8 @@ struct restitute_iterator_class<std::true_type /* total */,F,T>
   F f;
 };
 
-template<typename F>
-struct restitute_iterator_class<std::false_type /* non total */,F>
+template<typename IsTotal,typename F>
+struct restitute_iterator_class<IsTotal,F>
 {
   restitute_iterator_class(const F& f):f(f){}
   

test/Jamfile.v2

@@ -35,5 +35,6 @@ test-suite "poly_collection" :
     [ run test_fixed_variant.cpp           test_fixed_variant_main.cpp           ]
     [ run test_insertion.cpp               test_insertion_main.cpp               ]
     [ run test_iterators.cpp               test_iterators_main.cpp               ]
+    [ run test_null_variant_collection.cpp test_null_variant_collection_main.cpp ]
     [ run test_registration.cpp            test_registration_main.cpp            ]
     ;

test/test_null_variant_collection.cpp

@@ -0,0 +1,73 @@
+/* Copyright 2024 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)
+ *
+ * See http://www.boost.org/libs/poly_collection for library home page.
+ */
+
+#include "test_null_variant_collection.hpp"
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/poly_collection/variant_collection.hpp>
+#include <boost/poly_collection/algorithm.hpp>
+#include <utility>
+#include "test_utilities.hpp"
+
+using namespace test_utilities;
+
+void test_null_variant_collection()
+{
+  using boost::poly_collection::unregistered_type;
+  using collection_type=boost::variant_collection_of<>;
+  using value_type=collection_type::value_type;
+
+  collection_type        c,c2{c},c3{std::move(c2)};
+  const collection_type& cc=c;
+
+  c2=c;
+  c=std::move(c2);
+
+  (void)c.get_allocator();
+
+  (void)c.begin();
+  (void)c.end();
+  (void)c.cbegin();
+  (void)c.cend();
+  check_throw<unregistered_type>(
+    [&]{(void)c.begin(0);},
+    [&]{(void)c.end(0);},
+    [&]{(void)c.cbegin(0);},
+    [&]{(void)c.cend(0);});
+
+  check_throw<unregistered_type>(
+    [&]{c.segment(0);},
+    [&]{cc.segment(0);});
+
+  for(auto seg:c.segment_traversal()){(void)seg;}
+  for(auto seg:cc.segment_traversal()){(void)seg;}
+
+  BOOST_TEST(cc.empty());
+  check_throw<unregistered_type>([&]{(void)cc.empty(0);});
+
+  BOOST_TEST_EQ(cc.size(),0);
+  check_throw<unregistered_type>([&]{(void)cc.size(0);});
+
+  check_throw<unregistered_type>([&]{(void)cc.capacity(0);});
+
+  c.shrink_to_fit();
+  check_throw<unregistered_type>([&]{(void)c.shrink_to_fit(0);});
+
+  c.clear();
+  check_throw<unregistered_type>([&]{(void)c.clear(0);});
+
+  c.swap(c);
+
+  BOOST_TEST(cc==cc);
+  BOOST_TEST(!(cc!=cc));
+
+  auto f=[](value_type&){};
+
+  boost::poly_collection::for_each(c.begin(),c.end(),f);
+  boost::poly_collection::for_each_n(c.begin(),0,f);
+}

test/test_null_variant_collection.hpp

@@ -0,0 +1,9 @@
+/* Copyright 2024 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)
+ *
+ * See http://www.boost.org/libs/poly_collection for library home page.
+ */
+
+void test_null_variant_collection();

test/test_null_variant_collection_main.cpp

@@ -0,0 +1,16 @@
+/* Copyright 2024 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)
+ *
+ * See http://www.boost.org/libs/poly_collection for library home page.
+ */
+
+#include <boost/core/lightweight_test.hpp>
+#include "test_null_variant_collection.hpp"
+
+int main()
+{
+  test_null_variant_collection();
+  return boost::report_errors();
+}