Alternatively, if you do not wish to support InputIterator semantics, it might be better to remove operator++(int) or have it return void instead of a conceptually invalid iterator. -- 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 From: Mueller-Roemer, Johannes Sebastian Sent: Monday, February 16, 2015 15:00 To: boost-users@lists.boost.org Subject: RE: [Boost-users] [context] boost::coroutines::asymmetric_coroutine<T>::pull_type iterator does not properly model InputIterator If that is „as expected“ it still violates the requirements for an InputIterator. See the last row in Table 107 in 24.2.3 in the standard http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4296.pdf As-is the current “iterator” is not a valid iterator of any kind as InputIterator is already the weakest requirement. Example of how it should work (using an istream_iterator, which is an InputIterator): #include <iostream> #include <sstream> #include <iterator> auto main(int, char **) -> int { std::istringstream str("Hello , World !"); for(auto it = std::istream_iterator<std::string>(str); it != std::istream_iterator<std::string>();) std::cout << *it++; std::cout << "\n"; } Which outputs (as expected): Hello,World! The issue can be solved by storing a value in the iterator or returning a proxy object which dereferences to the original value. -- 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<mailto:johannes.mueller-roemer@igd.fraunhofer.de> | www.igd.fraunhofer.de<http://www.igd.fraunhofer.de> From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Oliver Kowalke Sent: Monday, February 16, 2015 14:20 To: boost-users@lists.boost.org<mailto:boost-users@lists.boost.org> Subject: Re: [Boost-users] [context] boost::coroutines::asymmetric_coroutine<T>::pull_type iterator does not properly model InputIterator 2015-02-16 13:46 GMT+01:00 Mueller-Roemer, Johannes Sebastian <Johannes.Sebastian.Mueller-Roemer@igd.fraunhofer.de<mailto:Johannes.Sebastian.Mueller-Roemer@igd.fraunhofer.de>>: Compiling is not the issue. it works as expected Furthermore your example does not test the issue I mentioned, as it does not use *it++; operator++ has higher precedence than operator* -> each increment triggers an jump/switch operation -> last increment invalidates coroutine