diff --git a/include/boost/function/detail/prologue.hpp b/include/boost/function/detail/prologue.hpp
index 1028ec8..fd51cc7 100644
--- a/include/boost/function/detail/prologue.hpp
+++ b/include/boost/function/detail/prologue.hpp
@@ -2,6 +2,7 @@
 #define BOOST_FUNCTION_PROLOGUE_HPP
 #  include <cassert>
 #  include <algorithm>
+#  include <boost/throw_exception.hpp>
 #  include <boost/config.hpp>
 #  include <boost/function/function_base.hpp>
 #  include <boost/mem_fn.hpp>
diff --git a/include/boost/function/function_base.hpp b/include/boost/function/function_base.hpp
index ae61fda..52c07af 100644
--- a/include/boost/function/function_base.hpp
+++ b/include/boost/function/function_base.hpp
@@ -17,6 +17,7 @@
 #define BOOST_FUNCTION_BASE_HEADER
 
 #include <stdexcept>
+#include <string>
 #include <memory>
 #include <new>
 #include <boost/config.hpp>
@@ -255,52 +256,62 @@ namespace boost {
     } // end namespace function
   } // end namespace detail
 
-  /**
-   * The function_base class contains the basic elements needed for the
-   * function1, function2, function3, etc. classes. It is common to all
-   * functions (and as such can be used to tell if we have one of the
-   * functionN objects).
-   */
-  class function_base
+/**
+ * The function_base class contains the basic elements needed for the
+ * function1, function2, function3, etc. classes. It is common to all
+ * functions (and as such can be used to tell if we have one of the
+ * functionN objects).
+ */
+class function_base
+{
+public:
+  function_base() : manager(0)
   {
-  public:
-    function_base() : manager(0)
+    functor.obj_ptr = 0;
+  }
+
+  // Is this function empty?
+  bool empty() const { return !manager; }
+
+public: // should be protected, but GCC 2.95.3 will fail to allow access
+  detail::function::any_pointer (*manager)(
+    detail::function::any_pointer,
+    detail::function::functor_manager_operation_type);
+  detail::function::any_pointer functor;
+};
+
+/**
+ * The bad_function_call exception class is thrown when a boost::function
+ * object is invoked
+ */
+class bad_function_call : public std::runtime_error
+{
+public:
+  bad_function_call() : std::runtime_error("call to empty boost::function") {}
+};
+
+/* Poison comparison between Boost.Function objects (because it is
+ * meaningless). The comparisons would otherwise be allowed because of the
+ * conversion required to allow syntax such as:
+ *   boost::function<int, int> f;
+ *   if (f) { f(5); }
+ */
+void operator==(const function_base&, const function_base&);
+void operator!=(const function_base&, const function_base&);
+
+namespace detail {
+  namespace function {
+    inline bool has_empty_target(const function_base* f)
     {
-      functor.obj_ptr = 0;
+      return f->empty();
     }
 
-    // Is this function empty?
-    bool empty() const { return !manager; }
-
-  public: // should be protected, but GCC 2.95.3 will fail to allow access
-    detail::function::any_pointer (*manager)(
-                           detail::function::any_pointer,
-                           detail::function::functor_manager_operation_type);
-    detail::function::any_pointer functor;
-  };
-
-  /* Poison comparison between Boost.Function objects (because it is
-   * meaningless). The comparisons would otherwise be allowed because of the
-   * conversion required to allow syntax such as:
-   *   boost::function<int, int> f;
-   *   if (f) { f(5); }
-   */
-  void operator==(const function_base&, const function_base&);
-  void operator!=(const function_base&, const function_base&);
-
-  namespace detail {
-    namespace function {
-      inline bool has_empty_target(const function_base* f)
-      {
-        return f->empty();
-      }
-
-      inline bool has_empty_target(...)
-      {
-        return false;
-      }
-    } // end namespace function
-  } // end namespace detail
-}
+    inline bool has_empty_target(...)
+    {
+      return false;
+    }
+  } // end namespace function
+} // end namespace detail
+} // end namespace boost
 
 #endif // BOOST_FUNCTION_BASE_HEADER
diff --git a/include/boost/function/function_template.hpp b/include/boost/function/function_template.hpp
index 0630ec8..79a8a82 100644
--- a/include/boost/function/function_template.hpp
+++ b/include/boost/function/function_template.hpp
@@ -21,7 +21,6 @@
 
 #define BOOST_FUNCTION_TEMPLATE_ARGS BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS, T)
 
-
 #define BOOST_FUNCTION_PARM(J,I,D) BOOST_PP_CAT(T,I) BOOST_PP_CAT(a,I)
 
 #define BOOST_FUNCTION_PARMS BOOST_PP_ENUM(BOOST_FUNCTION_NUM_ARGS,BOOST_FUNCTION_PARM,BOOST_PP_EMPTY)
@@ -247,6 +246,13 @@ namespace boost {
   public:
     BOOST_STATIC_CONSTANT(int, args = BOOST_FUNCTION_NUM_ARGS);
 
+    // add signature for boost::lambda
+    template<typename Args>
+    struct sig
+    {
+      typedef internal_result_type type;
+    };
+
 #if BOOST_FUNCTION_NUM_ARGS == 1
     typedef T0 argument_type;
 #elif BOOST_FUNCTION_NUM_ARGS == 2
@@ -289,7 +295,8 @@ namespace boost {
 
     result_type operator()(BOOST_FUNCTION_PARMS) const
     {
-      assert(!this->empty());
+      if (this->empty())
+        boost::throw_exception(bad_function_call());
 
       internal_result_type result = invoker(function_base::functor
                                             BOOST_FUNCTION_COMMA
@@ -533,11 +540,6 @@ class function<BOOST_FUNCTION_PARTIAL_SPEC, Allocator>
                                   BOOST_FUNCTION_COMMA Allocator> base_type;
   typedef function self_type;
 
-  struct clear_type {};
-
-  class holder;
-  friend class holder;
-
 public:
   typedef typename base_type::allocator_type allocator_type;
 
@@ -548,44 +550,28 @@ public:
 
   function(const self_type& f) : base_type(static_cast<const base_type&>(f)){}
 
-  self_type& operator=(self_type& f)
+  function(const base_type& f) : base_type(static_cast<const base_type&>(f)){}
+
+  self_type& operator=(const self_type& f)
   {
     self_type(f).swap(*this);
     return *this;
   }
 
-  inline self_type& operator=(holder h);
-
-  self_type& operator=(clear_type*)
+  template<typename Functor>
+  self_type& operator=(Functor f)
   {
-    this->clear();
+    self_type(f).swap(*this);
+    return *this;
+  }
+
+  self_type& operator=(const base_type& f)
+  {
+    self_type(f).swap(*this);
     return *this;
   }
 };
 
-template<typename R BOOST_FUNCTION_COMMA
-         BOOST_FUNCTION_TEMPLATE_PARMS,
-         typename Allocator>
-class function<BOOST_FUNCTION_PARTIAL_SPEC, Allocator>::holder
-{
-public:
-  template<typename F> holder(F f) : func(f) {}
-  holder(const base_type& f) : func(f) {}
-  holder(const self_type& f) : func(f) {}
-
-  self_type func;
-};
-
-template<typename R BOOST_FUNCTION_COMMA
-         BOOST_FUNCTION_TEMPLATE_PARMS,
-         typename Allocator>
-function<BOOST_FUNCTION_PARTIAL_SPEC, Allocator>&
-function<BOOST_FUNCTION_PARTIAL_SPEC, Allocator>::operator=(holder h)
-{
-  h.func.swap(*this);
-  return *this;
-}
-
 #undef BOOST_FUNCTION_PARTIAL_SPEC
 #endif // have partial specialization
 
diff --git a/test/function_n_test.cpp b/test/function_n_test.cpp
index 34817bc..3e4e92f 100644
--- a/test/function_n_test.cpp
+++ b/test/function_n_test.cpp
@@ -76,7 +76,7 @@ test_zero_args()
 
   // clear() method
   v1.clear();
-  BOOST_TEST(v1.empty());
+  BOOST_TEST(v1 == 0);
 
   // Assignment to an empty function
   v1 = three;
diff --git a/test/function_test.cpp b/test/function_test.cpp
index 01cb5b0..706e9cf 100644
--- a/test/function_test.cpp
+++ b/test/function_test.cpp
@@ -20,6 +20,7 @@
 #include <functional>
 #include <cassert>
 #include <string>
+#include <utility>
 
 using namespace boost;
 using namespace std;
@@ -98,7 +99,7 @@ test_zero_args()
   BOOST_TEST(global_int == 5);
 
   // clear
-  v1 = 0;
+  v1.clear();
   BOOST_TEST(0 == v1);
 
   // Assignment to an empty function from a free function
@@ -696,6 +697,43 @@ static void test_allocator()
 #endif // ndef BOOST_NO_STD_ALLOCATOR
 }
 
+static void test_exception()
+{
+  boost::function<int (int, int)> f;
+  try {
+    f(5, 4);
+    BOOST_TEST(false);
+  }
+  catch(boost::bad_function_call) {
+    // okay
+  }
+}
+
+typedef boost::function< void * (void * reader) > reader_type;
+typedef std::pair<int, reader_type> mapped_type;
+
+static void test_implicit()
+{
+  mapped_type m;
+  m = mapped_type();
+}
+
+static void test_call_obj(boost::function<int (int, int)> f)
+{
+  assert(!f.empty());
+}
+
+static void test_call_cref(const boost::function<int (int, int)>& f)
+{
+  assert(!f.empty());
+}
+
+static void test_call()
+{
+  test_call_obj(std::plus<int>());
+  test_call_cref(std::plus<int>());
+}
+
 int test_main(int, char* [])
 {
   test_zero_args();
@@ -705,6 +743,9 @@ int test_main(int, char* [])
   test_member_functions();
   test_ref();
   test_allocator();
+  test_exception();
+  test_implicit();
+  test_call();
 
   return 0;
 }
diff --git a/test/lambda_test.cpp b/test/lambda_test.cpp
new file mode 100644
index 0000000..7b9e396
--- /dev/null
+++ b/test/lambda_test.cpp
@@ -0,0 +1,29 @@
+#include <iostream>
+#include <cstdlib>
+
+#include <boost/test/test_tools.hpp>
+#include <boost/lambda/lambda.hpp>
+#include <boost/lambda/bind.hpp>
+#include <boost/function.hpp>
+
+using namespace std;
+using namespace boost;
+using namespace boost::lambda;
+
+static unsigned
+func_impl(int arg1, bool arg2, double arg3)
+{
+  return abs (static_cast<int>((arg2 ? arg1 : 2 * arg1) * arg3));
+}
+
+int test_main(int, char*[])
+{
+  function <unsigned(bool, double)> f1 = bind(func_impl, 15, _1, _2);
+  function <unsigned(double)>       f2 = bind(f1, false, _1);
+  function <unsigned()>             f3 = bind(f2, 4.0);
+
+  unsigned result = f3();
+
+  return 0;
+}
+