The current standard doesn’t say so, but the intention is that y and z have the same type. There is an open Core Working Group issue for this: http://wg21.cmeerw.net/cwg/issue1286
To the best of my knowledge here’s what’s going on. DR228 says: [Voted into WP at April 2003 meeting.] Consider the following example: template<class T> struct X { virtual void f(); }; template<class T> struct Y { void g(X<T> *p) { p->template X<T>::f(); } }; This is an error because X is not a member … Read more
I would like to argue that the Standard does not support SFINAE in partial specializations, due to a wording defect. Let’s start with [temp.class.spec.match]: A partial specialization matches a given actual template argument list if the template arguments of the partial specialization can be deduced from the actual template argument list (14.8.2). And, from [temp.deduct], … Read more
There is a Django Snippet which provides a solution: # settings.py class InvalidVarException(object): def __mod__(self, missing): try: missing_str=unicode(missing) except: missing_str=”Failed to create string representation” raise Exception(‘Unknown template variable %r %s’ % (missing, missing_str)) def __contains__(self, search): if search==’%s’: return True return False TEMPLATE_DEBUG=True TEMPLATE_STRING_IF_INVALID = InvalidVarException()
This is core issue 728, which was filed before generic lambdas were a thing. You mentioned generic lambdas and that they were identical to local classes with corresponding member template operator(). However, they actually aren’t, and the differences are related to implementation characteristics. Consider template <typename T> class X { template <typename> void foo() { … Read more
Well, it’s not possible. No way to make it call .width each time again. But you can use boost, of course: #include <boost/function_output_iterator.hpp> #include <boost/lambda/lambda.hpp> #include <algorithm> #include <iostream> #include <iomanip> int main() { using namespace boost::lambda; int a[] = { 1, 2, 3, 4 }; std::copy(a, a + 4, boost::make_function_output_iterator( var(std::cout) << std::setw(3) << … Read more
The 2nd template parameter of std::set expects a type, not an expression, so it is just you are using it wrongly. You could create the set like this: auto comp = [](const A& lhs, const A& rhs) -> bool { return lhs.x < rhs.x; }; auto SetOfA = std::set <A, decltype(comp)> (comp);
There is indeed a way for non-final non-union class types: namespace detail { struct P {typedef int member;}; template <typename U> struct test_for_member : U, P { template <typename T=test_for_member, typename = typename T::member> static std::false_type test(int); static std::true_type test(float); }; } template <typename T> using test_for_member = std::integral_constant<bool, decltype(detail::test_for_member<T>::test(0)){}>; Demo. The trick is to … Read more
I’ve just done a bit of research on this for our own nefarious purposes, and found the answer. You need to create an Eclipse plugin that uses the org.eclipse.ui.newWizards package. You can define your own category or use an existing one once you find the category ID. To create a new project wizard rather than … Read more
Yes. The static member is declared or defined inside the template< … > class { … } block. If it is declared but not defined, then there must be another declaration which provides the definition of the member. template< typename T > class has_static { // inline method definition: provides the body of the function. … Read more