Add is_*_iterator_v variable templates in C++14 and later.

.github/workflows/ci.yml

@@ -297,7 +297,7 @@ jobs:
             cxxstd: "11,14,17,20,2b"
             os: macos-14
           - toolset: clang
-            cxxstd: "11,14,17,20,2b"
+            cxxstd: "11,14,17,20,23"
             os: macos-15
 
           - name: CMake tests

include/boost/iterator/is_iterator.hpp

@@ -139,10 +139,19 @@ struct is_iterator< volatile T > : public detail::is_iterator_impl< T >::type {}
 template< typename T >
 struct is_iterator< const volatile T > : public detail::is_iterator_impl< T >::type {};
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+template< typename T >
+BOOST_INLINE_VARIABLE constexpr bool is_iterator_v = iterators::is_iterator< T >::value;
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
 } // namespace iterators
 
 using iterators::is_iterator;
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+using iterators::is_iterator_v;
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
 } // namespace boost
 
 #endif // BOOST_ITERATOR_IS_ITERATOR_HPP_INCLUDED_

include/boost/iterator/is_lvalue_iterator.hpp

@@ -4,6 +4,7 @@
 #ifndef IS_LVALUE_ITERATOR_DWA2003112_HPP
 #define IS_LVALUE_ITERATOR_DWA2003112_HPP
 
+#include <boost/config.hpp>
 #include <boost/iterator/detail/type_traits/conjunction.hpp>
 
 #include <iterator>
@@ -71,11 +72,23 @@ struct is_non_const_lvalue_iterator :
 {
 };
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+template< typename T >
+BOOST_INLINE_VARIABLE constexpr bool is_lvalue_iterator_v = iterators::is_lvalue_iterator< T >::value;
+template< typename T >
+BOOST_INLINE_VARIABLE constexpr bool is_non_const_lvalue_iterator_v = iterators::is_non_const_lvalue_iterator< T >::value;
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
 } // namespace iterators
 
 using iterators::is_lvalue_iterator;
 using iterators::is_non_const_lvalue_iterator;
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+using iterators::is_lvalue_iterator_v;
+using iterators::is_non_const_lvalue_iterator_v;
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
 } // namespace boost
 
 #endif // IS_LVALUE_ITERATOR_DWA2003112_HPP

include/boost/iterator/is_readable_iterator.hpp

@@ -6,6 +6,7 @@
 
 #include <iterator>
 #include <type_traits>
+#include <boost/config.hpp>
 
 namespace boost {
 namespace iterators {
@@ -60,10 +61,19 @@ struct is_readable_iterator :
 {
 };
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+template< typename T >
+BOOST_INLINE_VARIABLE constexpr bool is_readable_iterator_v = iterators::is_readable_iterator< T >::value;
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
 } // namespace iterators
 
 using iterators::is_readable_iterator;
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+using iterators::is_readable_iterator_v;
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
 } // namespace boost
 
 #endif // IS_READABLE_ITERATOR_DWA2003112_HPP

test/is_iterator.cpp

@@ -17,6 +17,7 @@
 #include <vector>
 #include <string>
 #include <iterator>
+#include <boost/config.hpp>
 #include <boost/iterator/iterator_adaptor.hpp>
 #include <boost/core/lightweight_test.hpp>
 
@@ -160,5 +161,25 @@ int main()
     BOOST_TEST(!boost::iterators::is_iterator< int (&)(int) >::value);
     BOOST_TEST(!boost::iterators::is_iterator< int (&)[10] >::value);
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+    BOOST_TEST(boost::iterators::is_iterator_v< int* >);
+    BOOST_TEST(boost::iterators::is_iterator_v< const int* >);
+    BOOST_TEST(boost::iterators::is_iterator_v< complete* >);
+    BOOST_TEST(boost::iterators::is_iterator_v< std::reverse_iterator< int* > >);
+    BOOST_TEST(boost::iterators::is_iterator_v< std::reverse_iterator< complete* > >);
+    BOOST_TEST(boost::iterators::is_iterator_v< adapted_iterator< int* > >);
+
+    BOOST_TEST(!boost::iterators::is_iterator_v< int >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< void* >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int (int) >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int (*)(int) >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int complete::* >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int (complete::*)(int) >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int*[] >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int*[10] >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int& >);
+    BOOST_TEST(!boost::iterators::is_iterator_v< int*& >);
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
     return boost::report_errors();
 }

test/is_lvalue_iterator.cpp

@@ -2,11 +2,12 @@
 // subject to 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 <boost/iterator/is_lvalue_iterator.hpp>
 #include <deque>
 #include <iterator>
 #include <cstddef> // std::ptrdiff_t
+#include <boost/config.hpp>
 #include <boost/noncopyable.hpp>
-#include <boost/iterator/is_lvalue_iterator.hpp>
 
 struct v
 {
@@ -168,5 +169,25 @@ int main()
     static_assert(!boost::is_non_const_lvalue_iterator<constant_lvalue_iterator<float>>::value,
                   "boost::is_non_const_lvalue_iterator<constant_lvalue_iterator<float>>::value is expected to be false.");
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+    static_assert(boost::is_lvalue_iterator_v<v*>,
+                  "boost::is_lvalue_iterator_v<v*> is expected to be true.");
+    static_assert(boost::is_lvalue_iterator_v<v const*>,
+                  "boost::is_lvalue_iterator_v<v const*> is expected to be true.");
+    static_assert(!boost::is_lvalue_iterator_v<proxy_iterator<int>>,
+                  "boost::is_lvalue_iterator_v<proxy_iterator<int>> is expected to be false.");
+    static_assert(!boost::is_lvalue_iterator_v<value_iterator>,
+                  "boost::is_lvalue_iterator_v<value_iterator> is expected to be false.");
+
+    static_assert(boost::is_non_const_lvalue_iterator_v<v*>,
+                  "boost::is_non_const_lvalue_iterator_v<v*> is expected to be true.");
+    static_assert(!boost::is_non_const_lvalue_iterator_v<v const*>,
+                  "boost::is_non_const_lvalue_iterator_v<v const*> is expected to be false.");
+    static_assert(!boost::is_non_const_lvalue_iterator_v<proxy_iterator<int>>,
+                  "boost::is_non_const_lvalue_iterator_v<proxy_iterator<int>> is expected to be false.");
+    static_assert(!boost::is_non_const_lvalue_iterator_v<value_iterator>,
+                  "boost::is_non_const_lvalue_iterator_v<value_iterator> is expected to be false.");
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
     return 0;
 }

test/is_readable_iterator.cpp

@@ -2,11 +2,12 @@
 // subject to 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 <boost/iterator/is_readable_iterator.hpp>
 #include <deque>
 #include <iterator>
 #include <cstddef> // std::ptrdiff_t
+#include <boost/config.hpp>
 #include <boost/noncopyable.hpp>
-#include <boost/iterator/is_readable_iterator.hpp>
 
 struct v
 {
@@ -97,5 +98,16 @@ int main()
     static_assert(boost::is_readable_iterator<noncopyable_iterator>::value,
                   "boost::is_readable_iterator<noncopyable_iterator>::value is expected to be true.");
 
+#if !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+    static_assert(boost::is_readable_iterator_v<v*>,
+                  "boost::is_readable_iterator_v<v*> is expected to be true.");
+    static_assert(boost::is_readable_iterator_v<v const*>,
+                  "boost::is_readable_iterator_v<v const*> is expected to be true.");
+    static_assert(boost::is_readable_iterator_v<proxy_iterator>,
+                  "boost::is_readable_iterator_v<proxy_iterator> is expected to be true.");
+    static_assert(!boost::is_readable_iterator_v<proxy_iterator2>,
+                  "boost::is_readable_iterator_v<proxy_iterator2> is expected to be false.");
+#endif // !defined(BOOST_NO_CXX14_VARIABLE_TEMPLATES)
+
     return 0;
 }