Fixed range adaptors that were creating underlying iterators that were not default constructible.

include/boost/range/detail/default_constructible_unary_fn.hpp

@@ -0,0 +1,64 @@
+// Boost.Range library
+//
+//  Copyright Neil Groves 2014. Use, modification and
+//  distribution is subject to the Boost Software License, Version
+//  1.0. (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// For more information, see http://www.boost.org/libs/range/
+//
+#ifndef BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
+#define BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
+
+#include <boost/optional/optional.hpp>
+#include <boost/mpl/if.hpp>
+#include <boost/type_traits/has_trivial_constructor.hpp>
+
+namespace boost
+{
+    namespace range_detail
+    {
+
+template<typename F, typename R>
+class default_constructible_unary_fn_wrapper
+{
+public:
+    typedef R result_type;
+
+    default_constructible_unary_fn_wrapper()
+    {
+    }
+    default_constructible_unary_fn_wrapper(const F& source)
+        : m_impl(source)
+    {
+    }
+    template<typename Arg>
+    R operator()(const Arg& arg) const
+    {
+        BOOST_ASSERT(m_impl);
+        return (*m_impl)(arg);
+    }
+    template<typename Arg>
+    R operator()(Arg& arg) const
+    {
+        BOOST_ASSERT(m_impl);
+        return (*m_impl)(arg);
+    }
+private:
+    boost::optional<F> m_impl;
+};
+
+template<typename F, typename R>
+struct default_constructible_unary_fn_gen
+{
+    typedef typename boost::mpl::if_<
+        boost::has_trivial_default_constructor<F>,
+        F,
+        default_constructible_unary_fn_wrapper<F,R>
+    >::type type;
+};
+
+    } // namespace range_detail
+} // namespace boost
+
+#endif // include guard