Update boost::apply to use variadics and perfect forwarding; refs #26

include/boost/bind/apply.hpp

@@ -11,6 +11,8 @@
 // http://www.boost.org/LICENSE_1_0.txt)
 //
 
+#include <boost/config.hpp>
+
 namespace boost
 {
 
@@ -18,6 +20,15 @@ template<class R> struct apply
 {
     typedef R result_type;
 
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+
+    template<class F, class... A> result_type operator()( F&& f, A&&... a ) const
+    {
+        return static_cast<F&&>( f )( static_cast<A&&>( a )... );
+    }
+
+#else
+
     template<class F> result_type operator()(F & f) const
     {
         return f();
@@ -67,6 +78,8 @@ template<class R> struct apply
     {
         return f(a1, a2, a3, a4, a5, a6, a7, a8, a9);
     }
+
+#endif
 };
 
 } // namespace boost

test/Jamfile.v2

@@ -81,3 +81,4 @@ run bind_noexcept_mf2_test.cpp ;
 run std_placeholders_test.cpp ;
 run apply_test.cpp ;
 run apply_test2.cpp ;
+run apply_rv_test.cpp ;

test/apply_rv_test.cpp

@@ -0,0 +1,77 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include<boost/bind/apply.hpp>
+#include<boost/bind/bind.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_NO_CXX11_RVALUE_REFERENCES is defined")
+int main() {}
+
+#elif defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_NO_CXX11_VARIADIC_TEMPLATES is defined")
+int main() {}
+
+#else
+
+struct F
+{
+public:
+
+    int operator()( int & x ) const
+    {
+        return x;
+    }
+
+    int operator()( int && x ) const
+    {
+        return -x;
+    }
+};
+
+int& get_lvalue_arg()
+{
+    static int a = 1;
+    return a;
+}
+
+int get_prvalue_arg()
+{
+    return 2;
+}
+
+F& get_lvalue_f()
+{
+    static F f;
+    return f;
+}
+
+F get_prvalue_f()
+{
+    return F();
+}
+
+int main()
+{
+    using namespace boost::placeholders;
+
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(get_lvalue_f), boost::bind(get_lvalue_arg))(), 1 );
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(get_lvalue_f), boost::bind(get_prvalue_arg))(), -2 );
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(get_prvalue_f), boost::bind(get_lvalue_arg))(), 1 );
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(get_prvalue_f), boost::bind(get_prvalue_arg))(), -2 );
+
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(boost::apply<F&>(), _1), boost::bind(boost::apply<int&>(), _2))(get_lvalue_f, get_lvalue_arg), 1 );
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(boost::apply<F&>(), _1), boost::bind(boost::apply<int>(), _2))(get_lvalue_f, get_prvalue_arg), -2 );
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(boost::apply<F>(), _1), boost::bind(boost::apply<int&>(), _2))(get_prvalue_f, get_lvalue_arg), 1 );
+    BOOST_TEST_EQ( boost::bind(boost::apply<int>(), boost::bind(boost::apply<F>(), _1), boost::bind(boost::apply<int>(), _2))(get_prvalue_f, get_prvalue_arg), -2 );
+
+    return boost::report_errors();
+}
+
+#endif