Ticket #3114: parameter_interface.patch

boost/parameter/aux_/tagged_argument.hpp

@@ -99 +99 @@
     typename result_of0<F>::type 
     get_with_lazy_default(lazy_default<KW,F> const& x, int) const
     {
-        return x.compute_default();
+        return x.compute_default(0);
     }
 
     template <class F>
@@ -140 +140 @@
     template <class KW, class F>
     typename result_of0<F>::type operator[](lazy_default<KW,F> const& x) const
     {
-        return x.compute_default();
+        return x.compute_default(0);
     }
 
     template <class ParameterRequirements>

boost/parameter/aux_/arg_list.hpp

@@ -114 +114 @@
     typename result_of0<F>::type
     get(lazy_default<K,F> x) const
     {
-        return x.compute_default();
+        return x.compute_default(0);
     }
 #endif
 
@@ -135 +135 @@
     operator[](
         BOOST_PARAMETER_lazy_default_fallback<K,F> x) const
     {
-        return x.compute_default();
+        return x.compute_default(0);
     }
 
     // No argument corresponding to ParameterRequirements::key_type

boost/parameter/aux_/default.hpp

@@ -52 +52 @@
   };
 #  define BOOST_PARAMETER_lazy_default_fallback lazy_default_base
 # else 
+template <typename DefaultComputer, typename T, typename Enable = void>
+struct use_template_call_helper {};
+
+template <typename DefaultComputer, typename T>
+struct use_template_call_helper<DefaultComputer, T,
+                                typename
+                                  DefaultComputer
+                                    ::boost_parameter_use_nested_template> {
+  typedef typename boost::result_of<DefaultComputer()>::type type;
+};
+
 template <class KW, class DefaultComputer>
 struct lazy_default
 {
     lazy_default(const DefaultComputer& x)
-      : compute_default(x)
+      : compute_default_obj(x)
     {}
-    DefaultComputer const& compute_default;
+    DefaultComputer const& compute_default_obj;
+
+    template <typename T>
+    typename boost::result_of<DefaultComputer()>::type
+    compute_default(T, ...) const {
+      return compute_default_obj();
+    }
+
+    template <typename T>
+    typename use_template_call_helper<DefaultComputer, T>::type
+    compute_default(T) const {
+      return compute_default_obj(0);
+    }
 };
 #  define BOOST_PARAMETER_lazy_default_fallback lazy_default
 # endif