Subject: [Boost-commit] svn:boost r56581 - trunk/boost/spirit/home/support
From: hartmut.kaiser_at_[hidden]
Date: 2009-10-04 17:19:12
Author: hkaiser
Date: 2009-10-04 17:19:12 EDT (Sun, 04 Oct 2009)
New Revision: 56581
URL: http://svn.boost.org/trac/boost/changeset/56581
Log:
Spirit: fixing transform_attribute::post for the generic case
Text files modified:
trunk/boost/spirit/home/support/attributes.hpp | 23 ++++++++++++++++++++++-
1 files changed, 22 insertions(+), 1 deletions(-)
Modified: trunk/boost/spirit/home/support/attributes.hpp
==============================================================================
--- trunk/boost/spirit/home/support/attributes.hpp (original)
+++ trunk/boost/spirit/home/support/attributes.hpp 2009-10-04 17:19:12 EDT (Sun, 04 Oct 2009)
@@ -25,6 +25,7 @@
#include <boost/fusion/include/for_each.hpp>
#include <boost/utility/value_init.hpp>
#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/is_convertible.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/end.hpp>
#include <boost/mpl/find_if.hpp>
@@ -312,12 +313,32 @@
// attributes. This template can be used as a customization point, where
// the user is able specify specific transformation rules for any attribute
// type.
+ //
+ // The default attribute transformation where the exposed attribute type is
+ // different from the required transformed attribute type relies on the
+ // convertibility exposed type --> transformed type, which is needed to
+ // successfully execute the pre transform step.
template <typename Exposed, typename Transformed, typename Enable/* = void*/>
struct transform_attribute
{
typedef Transformed type;
static Transformed pre(Exposed& val) { return Transformed(val); }
- static void post(Exposed&, Transformed const&) {}
+
+ static void post(Exposed&, Transformed const&, mpl::false_)
+ {
+ }
+ static void post(Exposed& val, Transformed const& attr, mpl::true_)
+ {
+ assign_to(attr, val);
+ }
+
+ // By default do post transform only if types are convertible,
+ // otherwise we assume no post transform is required (i.e. the user
+ // utilizes nview et.al.).
+ static void post(Exposed& val, Transformed const& attr)
+ {
+ post(val, attr, is_convertible<Transformed, Exposed>());
+ }
};
// The default is not to do any transformation