From a6e5e717fc2cb2dea03ba8105c07ded91daa57b5 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Thu, 21 Mar 2024 19:37:07 +0200
Subject: [PATCH] Add boost::compat::invoke

---
 include/boost/compat/detail/returns.hpp | 10 +++++++
 include/boost/compat/invoke.hpp         | 26 ++++++++++++++++++
 include/boost/compat/mem_fn.hpp         | 18 +++++++++++++
 test/Jamfile                            |  3 +++
 test/invoke_fn_test.cpp                 | 36 +++++++++++++++++++++++++
 5 files changed, 93 insertions(+)
 create mode 100644 include/boost/compat/detail/returns.hpp
 create mode 100644 include/boost/compat/invoke.hpp
 create mode 100644 include/boost/compat/mem_fn.hpp
 create mode 100644 test/invoke_fn_test.cpp

diff --git a/include/boost/compat/detail/returns.hpp b/include/boost/compat/detail/returns.hpp
new file mode 100644
index 0000000..4e44974
--- /dev/null
+++ b/include/boost/compat/detail/returns.hpp
@@ -0,0 +1,10 @@
+#ifndef BOOST_COMPAT_DETAIL_RETURNS_HPP_INCLUDED
+#define BOOST_COMPAT_DETAIL_RETURNS_HPP_INCLUDED
+
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#define BOOST_COMPAT_RETURNS(...) noexcept(noexcept(__VA_ARGS__)) -> decltype(__VA_ARGS__) { return __VA_ARGS__; }
+
+#endif // BOOST_COMPAT_DETAIL_RETURNS_HPP_INCLUDED
diff --git a/include/boost/compat/invoke.hpp b/include/boost/compat/invoke.hpp
new file mode 100644
index 0000000..7a67095
--- /dev/null
+++ b/include/boost/compat/invoke.hpp
@@ -0,0 +1,26 @@
+#ifndef BOOST_COMPAT_INVOKE_HPP_INCLUDED
+#define BOOST_COMPAT_INVOKE_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/mem_fn.hpp>
+#include <boost/compat/detail/returns.hpp>
+#include <utility>
+
+namespace boost {
+namespace compat {
+
+template<class F, class... A>
+auto invoke( F&& f, A&&... a )
+BOOST_COMPAT_RETURNS( std::forward<F>(f)(std::forward<A>(a)...) )
+
+template<class M, class T, class... A>
+auto invoke( M T::* pm, A&&... a )
+BOOST_COMPAT_RETURNS( mem_fn(pm)(std::forward<A>(a)...) )
+
+} // namespace compat
+} // namespace boost
+
+#endif // BOOST_COMPAT_INVOKE_HPP_INCLUDED
diff --git a/include/boost/compat/mem_fn.hpp b/include/boost/compat/mem_fn.hpp
new file mode 100644
index 0000000..3044a67
--- /dev/null
+++ b/include/boost/compat/mem_fn.hpp
@@ -0,0 +1,18 @@
+#ifndef BOOST_COMPAT_MEM_FN_HPP_INCLUDED
+#define BOOST_COMPAT_MEM_FN_HPP_INCLUDED
+
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <functional>
+
+namespace boost {
+namespace compat {
+
+using std::mem_fn;
+
+} // namespace compat
+} // namespace boost
+
+#endif // BOOST_COMPAT_MEM_FN_HPP_INCLUDED
diff --git a/test/Jamfile b/test/Jamfile
index feb3106..f4fb748 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -25,5 +25,8 @@ project
 run quick.cpp ;
 
 run latch_test.cpp ;
+
 run shared_lock_test.cpp ;
 run shared_lock_test.cpp : : : <exception-handling>off : shared_lock_test_nx ;
+
+run invoke_fn_test.cpp ;
diff --git a/test/invoke_fn_test.cpp b/test/invoke_fn_test.cpp
new file mode 100644
index 0000000..3cbc78e
--- /dev/null
+++ b/test/invoke_fn_test.cpp
@@ -0,0 +1,36 @@
+// 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/core/lightweight_test.hpp>
+
+int f0()
+{
+    return -1;
+}
+
+int f1( int x1 )
+{
+    return x1;
+}
+
+int f2( int x1, int x2 )
+{
+    return 10*x1+x2;
+}
+
+int f3( int x1, int x2, int x3 )
+{
+    return 100*x1 + 10*x2 + x3;
+}
+
+int main()
+{
+    BOOST_TEST_EQ( boost::compat::invoke( f0 ), -1 );
+    BOOST_TEST_EQ( boost::compat::invoke( f1, 1 ), 1 );
+    BOOST_TEST_EQ( boost::compat::invoke( f2, 1, 2 ), 12 );
+    BOOST_TEST_EQ( boost::compat::invoke( f3, 1, 2, 3 ), 123 );
+
+    return boost::report_errors();
+}