From 7ca2310b15e387258e97e4cd16887f5ee4906b28 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sun, 3 Sep 2023 17:55:50 +0300
Subject: [PATCH] Support fn.contains(f) where f is a function. Fixes #46.

---
 include/boost/function/function_base.hpp | 17 +++++++++++-
 test/Jamfile.v2                          |  3 +++
 test/contains3_test.cpp                  | 33 ++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 test/contains3_test.cpp

diff --git a/include/boost/function/function_base.hpp b/include/boost/function/function_base.hpp
index 5693e11e..00c7ce8e 100644
--- a/include/boost/function/function_base.hpp
+++ b/include/boost/function/function_base.hpp
@@ -25,6 +25,7 @@
 #include <boost/type_traits/alignment_of.hpp>
 #include <boost/type_traits/enable_if.hpp>
 #include <boost/type_traits/integral_constant.hpp>
+#include <boost/type_traits/is_function.hpp>
 #include <boost/assert.hpp>
 #include <boost/config.hpp>
 #include <boost/config/workaround.hpp>
@@ -652,7 +653,8 @@ class function_base
     }
 
   template<typename F>
-    bool contains(const F& f) const
+    typename boost::enable_if_< !boost::is_function<F>::value, bool >::type
+	contains(const F& f) const
     {
       if (const F* fp = this->template target<F>())
       {
@@ -662,6 +664,19 @@ class function_base
       }
     }
 
+  template<typename Fn>
+    typename boost::enable_if_< boost::is_function<Fn>::value, bool >::type
+	contains(Fn& f) const
+    {
+      typedef Fn* F;
+      if (const F* fp = this->template target<F>())
+      {
+        return function_equal(*fp, &f);
+      } else {
+        return false;
+      }
+    }
+
 #if defined(__GNUC__) && __GNUC__ == 3 && __GNUC_MINOR__ <= 3
   // GCC 3.3 and newer cannot copy with the global operator==, due to
   // problems with instantiation of function return types before it
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 15d401ea..7be87a11 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -90,3 +90,6 @@ run fn_eq_bind_test.cpp ;
 # /usr/include/c++/4.4/bits/shared_ptr.h:146: error: cannot use typeid with -fno-rtti
 run contains_test.cpp : : : <rtti>off <toolset>gcc-4.4,<cxxstd>0x:<build>no : contains_test_no_rtti ;
 run contains2_test.cpp : : : <rtti>off <toolset>gcc-4.4,<cxxstd>0x:<build>no : contains2_test_no_rtti ;
+
+run contains3_test.cpp ;
+run contains3_test.cpp : : : <rtti>off <toolset>gcc-4.4,<cxxstd>0x:<build>no : contains3_test_no_rtti ;
diff --git a/test/contains3_test.cpp b/test/contains3_test.cpp
new file mode 100644
index 00000000..e6130bbe
--- /dev/null
+++ b/test/contains3_test.cpp
@@ -0,0 +1,33 @@
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/function.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+static int f()
+{
+    return 1;
+}
+
+static int g()
+{
+    return 2;
+}
+
+int main()
+{
+    {
+        boost::function<int()> fn;
+        BOOST_TEST( !fn.contains( f ) );
+        BOOST_TEST( !fn.contains( g ) );
+    }
+
+    {
+        boost::function<int()> fn( f );
+        BOOST_TEST( fn.contains( f ) );
+        BOOST_TEST( !fn.contains( g ) );
+    }
+
+    return boost::report_errors();
+}