#include <iostream> #include <iterator> #include <string> #include <utility> #include <boost/coroutine/all.hpp> #include <boost/range/begin.hpp> #include <boost/range/end.hpp> template<typename Continuation> void bar(Continuation && yield) { yield("Hello"); yield(", "); yield("World"); yield("!\n"); } using T = std::string; using coro_t = boost::coroutines::asymmetric_coroutine<T>; coro_t::pull_type foo() { return coro_t::pull_type{ [](coro_t::push_type& yield) { bar(std::forward<coro_t::push_type>(yield)); }}; } int main(int, char **) { auto f = foo(); for ( auto i = boost::begin( f); i != boost::end( f); ++i) { std::cout << * i << std::endl; } return 0; } compiles with master branch 2015-02-16 9:22 GMT+01:00 Mueller-Roemer, Johannes Sebastian < Johannes.Sebastian.Mueller-Roemer@igd.fraunhofer.de>:
I’m currently on Boost 1.56 so this might have been fixed by now, but in a simple test Boost.Coroutine fails to properly model the InputIterator concept, because *it++ does not conform to the operational semantics { T tmp = *it; ++it; return tmp; } required by the standard.
The failing program:
#include <boost/coroutine/asymmetric_coroutine.hpp>
#include <iostream>
template<typename Continuation>
auto foo(Continuation && yield) -> void
{
yield("Hello");
yield(", ");
yield("World");
yield("!\n");
}
//using T = char const *;
using T = std::string;
auto foo() -> boost::coroutines::asymmetric_coroutine<T>::pull_type
{
using namespace boost::coroutines;
return asymmetric_coroutine<T>::pull_type{
[](asymmetric_coroutine<T>::push_type& yield) { foo(yield); }
};
}
auto main(int, char **) -> int
{
auto f = foo();
for(auto it = boost::begin(f); it != boost::end(f);)
std::cout << *it++;
}
Which (on my machine) outputs:
, World!
X☺à r2 ` , ` , Ç2 Ç
Failing to model the InputIterator concept is bad, because then it isn’t any kind of standards-conforming iterator at all. Interestingly, if T is char const * and not std::string the program works as expected. Is there some other subtle bug at work here?
--
Johannes S. Mueller-Roemer, MSc
Wiss. Mitarbeiter - Interactive Engineering Technologies (IET)
Fraunhofer-Institut für Graphische Datenverarbeitung IGD
Fraunhoferstr. 5 | 64283 Darmstadt | Germany
Tel +49 6151 155-606 | Fax +49 6151 155-139
johannes.mueller-roemer@igd.fraunhofer.de | www.igd.fraunhofer.de
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