On 3/2/14, 3:01 PM, Neil Groves wrote:
Making the constructor overloads less greedy is definitely an improvement. This has been implemented and pushed to the "develop" branch.
Good, I did it also in my own copy, using the SInglePassRangeConcept and WriteableRangeConcept from boost/range/concept.hpp, for both the constructors and the assignment operators. It seems to help a lot.
I has to modify your test case in a number of ways to be able to reproduce the problem accurately without artificial breakage. Hopefully my changes to make your test-case work did not remove any of the conditions you were attempting to demonstrate.
I expected that. :) I'm still pretty new to mpl.
Exmaple:
#include <boost/variant.hpp> #include <boost/range.hpp> #include <boost/mpl/vector.hpp>
using namespace boost;
enum E { e1, e2, e3 };
typedef mpl::vector<E, std::string > args; typedef boost::make_variant_over<args>::type OkVariant;
typedef mpl::vector<boost::iterator_range<std::string::iterator>, args> args1;
args1 is not what you want for passing into the make_variant_over function since it is not an extended sequence as I think you intended. You need to do this:
typedef boost::mpl::push_back< args, boost::iterator_range<std::string::iterator> >::type args1;
Yup, discovered that a day or two after posting, thanks.
typedef boost::make_variant_over<args1>::type BrokenVariant;
int main(int argc, char **argv) { OkVariant ok; ok = e1; ok = "";
Your expression "" is of type const char[1]. Depending on the compiler this might match overloads for char* due to old rules allowing interopability between string literals and mutable char pointers and arrays. It is valid for a standard library implementation to implement the std::string::iterator as char*. If all these factors conspire against you then even with the updates in the "develop" branch you will suffer ambiguous function calls.
Ah, true. I've fallen into the problem that template argument deduction doesn't work like function overloading resolution...there's no use or ranking of conversions. I've learned a lot in the last week or too, and moved past this trouble. Thanks for your help. -- Jon Biggar jon@floorboard.com jon@biggar.org jonbiggar@gmail.com