Add bind_back

boostorg · Mar 29, 2024 · 9a58caf · 9a58caf
1 parent 28e7155
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diff --git a/include/boost/compat/bind_back.hpp b/include/boost/compat/bind_back.hpp
@@ -0,0 +1,72 @@
+#ifndef BOOST_COMPAT_BIND_BACK_HPP_INCLUDED
+#define BOOST_COMPAT_BIND_BACK_HPP_INCLUDED
+
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/compat/invoke.hpp>
+#include <boost/compat/type_traits.hpp>
+#include <boost/compat/integer_sequence.hpp>
+#include <boost/compat/detail/returns.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+#include <tuple>
+#include <utility>
+
+namespace boost {
+namespace compat {
+
+namespace detail {
+
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1910)
+# pragma warning(push)
+# pragma warning(disable: 4100) // 'a': unreferenced formal parameter
+#endif
+
+template<class F, class A, class... B, std::size_t... I>
+static constexpr auto invoke_bind_back_( F&& f, A&& a, index_sequence<I...>, B&&... b )
+    BOOST_COMPAT_RETURNS( compat::invoke( std::forward<F>(f), std::forward<B>(b)..., std::get<I>( std::forward<A>(a) )... ) )
+
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1910)
+# pragma warning(pop)
+#endif
+
+template<class F, class... A> class bind_back_
+{
+private:
+
+    F f_;
+    std::tuple<A...> a_;
+
+public:
+
+    template<class F2, class... A2>
+    constexpr bind_back_( F2&& f2, A2&&... a2 ): f_( std::forward<F2>(f2) ), a_( std::forward<A2>(a2)... ) {}
+
+public:
+
+    template<class... B> BOOST_CXX14_CONSTEXPR auto operator()( B&&... b ) &
+        BOOST_COMPAT_RETURNS( detail::invoke_bind_back_( f_, a_, make_index_sequence<sizeof...(A)>(), std::forward<B>(b)... ) )
+
+    template<class... B> constexpr auto operator()( B&&... b ) const &
+        BOOST_COMPAT_RETURNS( detail::invoke_bind_back_( f_, a_, make_index_sequence<sizeof...(A)>(), std::forward<B>(b)... ) )
+
+    template<class... B> BOOST_CXX14_CONSTEXPR auto operator()( B&&... b ) &&
+        BOOST_COMPAT_RETURNS( detail::invoke_bind_back_( std::move(f_), std::move(a_), make_index_sequence<sizeof...(A)>(), std::forward<B>(b)... ) )
+
+    template<class... B> constexpr auto operator()( B&&... b ) const &&
+        BOOST_COMPAT_RETURNS( detail::invoke_bind_back_( std::move(f_), std::move(a_), make_index_sequence<sizeof...(A)>(), std::forward<B>(b)... ) )
+};
+
+} // namespace detail
+
+template<class F, class... A> constexpr auto bind_back( F&& f, A&&... a ) -> detail::bind_back_< decay_t<F>, decay_t<A>... >
+{
+    return { std::forward<F>(f), std::forward<A>(a)... };
+}
+
+} // namespace compat
+} // namespace boost
+
+#endif // BOOST_COMPAT_BIND_BACK_HPP_INCLUDED
diff --git a/test/Jamfile b/test/Jamfile
@@ -64,3 +64,8 @@ compile bind_front_mfn_constexpr_test.cpp ;
 compile bind_front_md_constexpr_test.cpp ;
 
 run integer_sequence_test.cpp ;
+
+run bind_back_fn_test.cpp ;
+run bind_back_obj_test.cpp ;
+run bind_back_mfn_test.cpp ;
+run bind_back_md_test.cpp ;
diff --git a/test/bind_back_fn_test.cpp b/test/bind_back_fn_test.cpp
@@ -0,0 +1,57 @@
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(__GNUC__) && __GNUC__ == 7
+# pragma GCC diagnostic ignored "-Wnoexcept-type"
+#endif
+
+#include <boost/compat/bind_back.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <memory>
+
+int f0()
+{
+    return -1;
+}
+
+int f1( int x1 ) noexcept
+{
+    return x1;
+}
+
+int f2( int x1, int x2 )
+{
+    return 10*x1+x2;
+}
+
+int f3( int x1, int x2, int x3 ) noexcept
+{
+    return 100*x1 + 10*x2 + x3;
+}
+
+int g( std::unique_ptr<int> p, std::unique_ptr<int> q )
+{
+    return 10 * *p + *q;
+}
+
+int main()
+{
+    BOOST_TEST_EQ( boost::compat::bind_back( f0 )(), -1 );
+    BOOST_TEST_EQ( boost::compat::bind_back( f1 )( 1 ), 1 );
+    BOOST_TEST_EQ( boost::compat::bind_back( f2 )( 1, 2 ), 12 );
+    BOOST_TEST_EQ( boost::compat::bind_back( f3 )( 1, 2, 3 ), 123 );
+
+    BOOST_TEST_EQ( boost::compat::bind_back( f1, 1 )(), 1 );
+    BOOST_TEST_EQ( boost::compat::bind_back( f2, 1 )( 2 ), 21 );
+    BOOST_TEST_EQ( boost::compat::bind_back( f3, 1 )( 2, 3 ), 231 );
+
+    BOOST_TEST_EQ( boost::compat::bind_back( f2, 1, 2 )(), 12 );
+    BOOST_TEST_EQ( boost::compat::bind_back( f3, 1, 2 )( 3 ), 312 );
+
+    BOOST_TEST_EQ( boost::compat::bind_back( f3, 1, 2, 3 )(), 123 );
+
+    BOOST_TEST_EQ( boost::compat::bind_back( g, std::unique_ptr<int>( new int(1) ) )( std::unique_ptr<int>( new int(2) ) ), 21 );
+
+    return boost::report_errors();
+}
diff --git a/test/bind_back_md_test.cpp b/test/bind_back_md_test.cpp
@@ -0,0 +1,101 @@
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/compat/bind_back.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <functional>
+
+struct X
+{
+    int m = -1;
+};
+
+struct Y: public virtual X
+{
+};
+
+int main()
+{
+    {
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, X() )(), -1 );
+    }
+
+    {
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, Y() )(), -1 );
+    }
+
+    {
+        X x;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, x )(), -1 );
+    }
+
+    {
+        X x;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, &x )(), -1 );
+        boost::compat::bind_back( &X::m, &x )() = +1;
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, &x )(), +1 );
+    }
+
+    {
+        X x;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::ref(x) )(), -1 );
+        boost::compat::bind_back( &X::m, std::ref(x) )() = +1;
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::ref(x) )(), +1 );
+    }
+
+    {
+        X x;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::cref(x) )(), -1 );
+    }
+
+    {
+        Y y;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, y )(), -1 );
+    }
+
+    {
+        Y y;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, &y )(), -1 );
+        boost::compat::bind_back( &X::m, &y )() = +1;
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, &y )(), +1 );
+    }
+
+    {
+        Y y;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::ref(y) )(), -1 );
+        boost::compat::bind_back( &X::m, std::ref(y) )() = +1;
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::ref(y) )(), +1 );
+    }
+
+    {
+        Y y;
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::cref(y) )(), -1 );
+    }
+
+    {
+        X const x = {};
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, x )(), -1 );
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, &x )(), -1 );
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::ref(x) )(), -1 );
+    }
+
+    {
+        Y const y = {};
+
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, y )(), -1 );
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, &y )(), -1 );
+        BOOST_TEST_EQ( boost::compat::bind_back( &X::m, std::ref(y) )(), -1 );
+    }
+
+    return boost::report_errors();
+}