- Boost-users - lists.boost.org

Vector values gradients for vector -> scalar function
by Amit Gupta 25 Jan '22

25 Jan '22

I am currently exploring boost as autodiff framework for my application. I would like to calculate the derivative of a vector->scalar function. However I could not find a way to evaluate the same, rather I always get total gradient. Example: How to get the following program yield output equivalent to JAX fwd? #include <boost/math/differentiation/autodiff.hpp> #include <iostream> #include<vector> template <typename T> T power_sum(double p, std::vector<T> &z){ T y=0.0; for (int i=0; i<6;i++){ y += pow(z[i], p); } return y; } int main() { using namespace boost::math::differentiation; constexpr unsigned Order = 2; std::vector<double> z_v = {1.,2.,3.,4.,5.,6.}; std::vector<autodiff_fvar<double, Order> > z; for (int i=0; i<6;i++){ z.push_back(make_fvar<double, Order>(z_v[i])); } auto y = power_sum(2.0,z); std::cout<<y<<"\n"; std::cout<<y.derivative(1)<<"\n"; return 0; } JAX output: import jax as jx import jax.numpy as jnp x = jnp.array([1.0, 2.0, 3.0, 4.0, 5.0, 6.0]) def power_sum(x, p): y = x[0] ** p + x[1] ** p + x[2] ** p + x[3] ** p + x[4] ** p + x[5] ** p return y f_prime = jx.jacfwd(power_sum)(x,2.0) f_prime # DeviceArray([ 2., 4., 6., 8., 10., 12.], dtype=float32) I understand I can do it by send array 6 times with all other vvector values being zero. Is there a better way?

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Re: [Boost-users] casually blocked UDP port
by Alexander Carôt 17 Jan '22

17 Jan '22

Hello again, I'd consider using boost asio SO_REUSEPORT option in order to reuse the port if already taken according to this thread: https://stackoverflow.com/questions/34596638/boost-asio-so-reuseport I will try it asap but please let me know if you have concerns or better solutions. Thanks and best Alex P.S.: see below – I now know how to reproduce the issue: When my application does receive UDP streaming data I spontaneously quit the application. Then doing: "netstat -p UDP" shows me the following Proto Recv-Q Send-Q Local Address Foreign Address (state) udp4 1026 0 *.50050 *.* So, basically the receive queue for this socket is not empty and the previous bind port is indeed still there. If anyone has an idea how to proceed from here on please let me know but now I might be able to fix it myself already. Best Alex Thanks for the swift response, Andreas ! In fact I am aware of what you wrote but with regard to the conditions my app works under it is extremely unlikely that some other process is taking this port. However, the next step for me is to identify which process actually has taken it. In that regard a follow-up question: Once an application (which uses boost sockets) has shut down (for crash or other reasons) the local bind port is also automatically released, right ? In other words: Can the OS stick a port although the corresponding application is not existent anymore ? I've been assuming no so far but maybe I am mistaken so I just need confirmation. Thank you, best Alex -- http://www.carot.de Email : Alexander(a)Carot.de Tel.: +49 (0)177 5719797 > Gesendet: Samstag, 15. Januar 2022 um 23:46 Uhr > Von: "Andreas Wehrmann via Boost-users" <boost-users(a)lists.boost.org> > An: boost-users(a)lists.boost.org > Cc: "Andreas Wehrmann" <a.wehrmann(a)yandex.com> > Betreff: Re: [Boost-users] casually blocked UDP port > > Am 14.01.2022 um 22:50 schrieb Alexander Carôt via Boost-users: > > Hello all, > > > > I have a problem with a a casually blocked UDP bind port: My application uses UDP port 50050 and initiates the socket this way: > > > > So I am basically using bind port 50050 and if it fails I am increasing it by one until the bind suceeds. In most cases the bind to port 50050 works fine but casually after a relaunch of the app or a crash the bind port 50050 appears to be blocked which is why it increases to higher numbers. > > > > Hi, > be aware that UDP sockets may are opened and closed for sending a single > request only by many applications/services. > If the sending application doesn't care about the local port and leaves > it up to the OS to assign a local port number, > you may run into the situation that another application/service/daemon > is opening a UDP socket, > not caring about the local port and the OS happens to assign the port > number that you want to bind your own socket to. > > All the best, > Andreas > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > https://lists.boost.org/mailman/listinfo.cgi/boost-users >

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Re: [Boost-users] casually blocked UDP port
by Alexander Carôt 16 Jan '22

16 Jan '22

P.S.: see below – I now know how to reproduce the issue: When my application does receive UDP streaming data I spontaneously quit the application. Then doing: "netstat -p UDP" shows me the following Proto Recv-Q Send-Q Local Address Foreign Address (state) udp4 1026 0 *.50050 *.* So, basically the receive queue for this socket is not empty and the previous bind port is indeed still there. If anyone has an idea how to proceed from here on please let me know but now I might be able to fix it myself already. Best Alex Thanks for the swift response, Andreas ! In fact I am aware of what you wrote but with regard to the conditions my app works under it is extremely unlikely that some other process is taking this port. However, the next step for me is to identify which process actually has taken it. In that regard a follow-up question: Once an application (which uses boost sockets) has shut down (for crash or other reasons) the local bind port is also automatically released, right ? In other words: Can the OS stick a port although the corresponding application is not existent anymore ? I've been assuming no so far but maybe I am mistaken so I just need confirmation. Thank you, best Alex -- http://www.carot.de Email : Alexander(a)Carot.de Tel.: +49 (0)177 5719797 > Gesendet: Samstag, 15. Januar 2022 um 23:46 Uhr > Von: "Andreas Wehrmann via Boost-users" <boost-users(a)lists.boost.org> > An: boost-users(a)lists.boost.org > Cc: "Andreas Wehrmann" <a.wehrmann(a)yandex.com> > Betreff: Re: [Boost-users] casually blocked UDP port > > Am 14.01.2022 um 22:50 schrieb Alexander Carôt via Boost-users: > > Hello all, > > > > I have a problem with a a casually blocked UDP bind port: My application uses UDP port 50050 and initiates the socket this way: > > > > So I am basically using bind port 50050 and if it fails I am increasing it by one until the bind suceeds. In most cases the bind to port 50050 works fine but casually after a relaunch of the app or a crash the bind port 50050 appears to be blocked which is why it increases to higher numbers. > > > > Hi, > be aware that UDP sockets may are opened and closed for sending a single > request only by many applications/services. > If the sending application doesn't care about the local port and leaves > it up to the OS to assign a local port number, > you may run into the situation that another application/service/daemon > is opening a UDP socket, > not caring about the local port and the OS happens to assign the port > number that you want to bind your own socket to. > > All the best, > Andreas > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > https://lists.boost.org/mailman/listinfo.cgi/boost-users >

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casually blocked UDP port
by Alexander Carôt 16 Jan '22

16 Jan '22

Hello all, I have a problem with a a casually blocked UDP bind port: My application uses UDP port 50050 and initiates the socket this way: udp::resolver resolver(dFC->myIoService); int port = 50050; bool failed; do{ failed = false; udp::resolver::query query(udp::v4(), IPAddress, port); try { dFC->s = new udp::socket( dFC->myIoService, udp::endpoint(*resolver.resolve(query))); } catch (std::exception &e) { failed = true; int intPort = this->intConverter(port); intPort++; ostringstream conv; conv << intPort; port = conv.str(); cout << "new port: " << port << endl; } while (failed); So I am basically using bind port 50050 and if it fails I am increasing it by one until the bind suceeds. In most cases the bind to port 50050 works fine but casually after a relaunch of the app or a crash the bind port 50050 appears to be blocked which is why it increases to higher numbers. Now I wonder how the port can still be taken although the app has terminated and if there is way to force the app / the OS using port 50050 ? So far I have seen this on OSX only – on Windows and Linux I haven't noticed it yet. Thanks in advance for any pointer how to resolve my isse, best Alex -- http://www.carot.de Email : Alexander(a)Carot.de Tel.: +49 (0)177 5719797

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exception on boost serialization
by Alessio Mochi 13 Jan '22

13 Jan '22

Hello, I can't resolve my exception when I compile my qt project with visual studio 2022. Error C2039 'throw_exception': is not a member of 'boost' DentalCad E:\boost_1_78_0\boost\serialization\throw_exception.hpp 30 I tried a compile a small example and work correctly without exception. I don't understand how solve the problem. Have you a suggest? Thanks in advance.

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Communicating with MS SQL Server.
by Senthil Cheetancheri 12 Jan '22

12 Jan '22

Hi, Is there a Boost library to communicate with Microsoft SQLServer? I see there is a proposal for MySQL (https://anarthal.github.io/boost-mysql-docs/index.html) but can't seem to find anything for MS SQLServer. Any pointers would be appreciated. Thanks, Senthil.

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Clarification on statechart post_event vs process_event within react()
by John McCabe 10 Jan '22

10 Jan '22

Hi, Apologies if this has already been answered/clarified, but my search of the internet to try to get a definitive answer, at least one I recognised as being definitive, was unsuccessful. Below I have posted some source code, based on the stopwatch example from the tutorial, but using an 'external' object to delegate the actual handling of event stuff to and using the state, rather than simple_state base class, and some other tweaks. This is a cut down version of something that someone I work with has devised, but I just wanted to get a clear answer on whether process_event() should be getting called in cases like this. I think it probably should not since, in the code below, you change state (with a state object's destructor being executed) whilst you're executing that state's react(EvStartStop) function. If someone can confirm this is the correct interpretation that would be very much appreciated. Any questions, feel free to ask (BTW - I'm compiling for C++17) John PS - In case it's of any use, the output from running this code is: ------ Entered Active Entered Stopped Stopped - payload2 m_charValue: a Exited ~Stopped <<<--- This is the bit I don't like the look of because... Entered Running Active - payload2 m_charValue: a <<<--- ... this happens from the forward_event() call payload1 value1: 20 payload1 value2: 200.2 Exited ~Running Entered Stopped Exiting Program Exited ~Stopped Exited ~Active ------ If I swap the //*** comments to the doProcess() lines instead of doPost(), the output seems more sensible ------ Entered Active Entered Stopped Stopped - payload2 m_charValue: a Exited ~Stopped Entered Running Active - payload2 m_charValue: a payload1 value1: 20 payload1 value2: 200.2 Exited ~Running Entered Stopped Exiting Program Exited ~Stopped Exited ~Active ------ ========== code =========== #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/mpl/list.hpp> #include <iostream> #include <string> namespace sc = boost::statechart; namespace mpl = boost::mpl; // Forward declare a handler 'class' that's going to have activity delegated to it struct Handler; // Normal example start/stop and reset events struct EvStartStop : sc::event<EvStartStop> {}; struct EvReset : sc::event<EvReset> {}; // A couple of events that carry data with them struct EvPayload1 : sc::event<EvPayload1> { EvPayload1(int value1, double value2) : m_value1 { value1 }, m_value2 { value2 } {}; int m_value1 { 0 }; double m_value2 { 0.0 }; }; struct EvPayload2 : sc::event<EvPayload2> { EvPayload2(const char& charValue) : m_charValue { charValue } {}; char m_charValue { false }; }; // Back to the example bits struct Active; struct StopWatch : sc::state_machine<StopWatch, Active> { typedef sc::transition<EvReset, Active> reactions; // The extra 'handler' stuff void setHandler(Handler* handler) { m_handler = handler; }; Handler* getHandler() const { return m_handler; }; Handler* m_handler { nullptr }; // Used to make post_event() accessible from an external class...seems unpleasant, but... using sc::state_machine<StopWatch, Active>::post_event; }; // The implementation of the Handler class; created with a reference to a StopWatch object struct Handler { Handler(StopWatch& stopWatch) : m_stopWatch { stopWatch } {}; void doPost() { m_stopWatch.post_event(EvStartStop()); } void doProcess() { m_stopWatch.process_event(EvStartStop()); } StopWatch& m_stopWatch; }; struct Stopped; struct Active : sc::state<Active, StopWatch, Stopped> { Active(my_context ctx) : my_base { ctx } { std::cout << "Entered Active" << std::endl; }; ~Active() { std::cout << "Exited ~Active" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload1>, sc::custom_reaction<EvPayload2>, sc::transition<EvReset, Active>> reactions; sc::result react(const EvPayload1& payload1) { std::cout << "payload1 Event NOT HANDLED" << std::endl; return discard_event(); } sc::result react(const EvPayload2& payload2) { std::cout << "Active - payload2 m_charValue: " << payload2.m_charValue << std::endl; return discard_event(); } }; struct Running : sc::state<Running, Active> { Running(my_context ctx) : my_base { ctx } { std::cout << "Entered Running" << std::endl; }; ~Running() { std::cout << "Exited ~Running" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload1>, sc::transition<EvStartStop, Stopped>> reactions; sc::result react(const EvPayload1& payload1) { std::cout << "payload1 value1: " << payload1.m_value1 << std::endl; std::cout << "payload1 value2: " << payload1.m_value2 << std::endl; //***context<StopWatch>().getHandler()->doPost(); context<StopWatch>().getHandler()->doProcess(); return discard_event(); } }; struct Stopped : sc::state<Stopped, Active> { Stopped(my_context ctx) : my_base { ctx } { std::cout << "Entered Stopped" << std::endl; }; ~Stopped() { std::cout << "Exited ~Stopped" << std::endl; }; typedef mpl::list<sc::custom_reaction<EvPayload2>, sc::transition<EvStartStop, Running>> reactions; sc::result react(const EvPayload2& payload2) { std::cout << "Stopped - payload2 m_charValue: " << payload2.m_charValue << std::endl; //***context<StopWatch>().getHandler()->doPost(); context<StopWatch>().getHandler()->doProcess(); return forward_event(); } }; int main() { StopWatch myWatch; Handler myHandler(myWatch); myWatch.setHandler(&myHandler); myWatch.initiate(); myWatch.process_event(EvPayload2 { 'a' }); myWatch.process_event(EvPayload1 { 20, 200.2 }); std::cout << "Exiting Program" << std::endl; return 0; }

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boost.gil build failed with GCC11 and -std=c++20
by Qiang Ren 10 Jan '22

10 Jan '22

Hi, I am on ubuntu 20.04, I have GCC9.4 and 10.3 and 11.1 installed. I found that when set "-std=c++20", with gcc11, boost.gil will failed to build. Here is the simple test cpp to reproduce the issue: #include <sstream> #include <boost/gil.hpp> #include <boost/gil/extension/io/png.hpp> namespace gil = boost::gil; int main() { gil::rgb8_image_t img; std::stringstream buf(std::ios::in | std::ios::out | std::ios::binary); gil::read_and_convert_image(buf, img, gil::png_tag{}); return 0; } the build command is: g++ -o test test_gcc11_gil.cc -std=c++20 -I${THIRD_PARTY}/boost/boost_1_78_0 -L${THIRD_PARTY}/libpng/1.6.37/lib/ -lpng If replaced '-std=c++20' with '-std=c++17', the build would be OK, but with 'c++20', gcc 11 failed with the following errors: In file included from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/read.hpp:13, from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png.hpp:11, from test_gcc11_gil.cc:3: /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:576:32: error: expected unqualified-id before ‘)’ token 576 | image_read_info< png_tag >() | ^ /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:711:36: error: expected unqualified-id before ‘)’ token 711 | image_read_settings< png_tag >() | ^ In file included from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/read.hpp:21, from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png.hpp:11, from test_gcc11_gil.cc:3: /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/io/make_reader.hpp: In instantiation of ‘typename boost::gil::get_reader<String, FormatTag, ConversionPolicy>::type boost::gil::make_reader(Device&, const FormatTag&, const ConversionPolicy&, typename std::enable_if<typename boost::mp11::detail::mp_and_impl<boost::mp11::mp_list<boost::gil::detail::is_adaptable_input_device<FormatTag, Device, void>, boost::gil::is_format_tag<FormatTag> >, void>::type::value>::type*) [with Device = std::__cxx11::basic_stringstream<char>; FormatTag = boost::gil::png_tag; ConversionPolicy = boost::gil::detail::read_and_convert<boost::gil::default_color_converter>; typename boost::gil::get_reader<String, FormatTag, ConversionPolicy>::type = boost::gil::reader<boost::gil::detail::istream_device<boost::gil::png_tag>, boost::gil::png_tag, boost::gil::detail::read_and_convert<boost::gil::default_color_converter> >; typename std::enable_if<typename boost::mp11::detail::mp_and_impl<boost::mp11::mp_list<boost::gil::detail::is_adaptable_input_device<FormatTag, Device, void>, boost::gil::is_format_tag<FormatTag> >, void>::type::value>::type = void;typename boost::mp11::detail::mp_and_impl<boost::mp11::mp_list<boost::gil::detail::is_adaptable_input_device<FormatTag, Device, void>, boost::gil::is_format_tag<FormatTag> >, void>::type =std::integral_constant<bool, true>]’: /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/io/read_and_convert_image.hpp:263:34: required from ‘void boost::gil::read_and_convert_image(Device&, Image&, const FormatTag&, typename std::enable_if<typename boost::mp11::detail::mp_and_impl<boost::mp11::mp_list<boost::gil::detail::is_read_device<FormatTag, Device, void>, boost::gil::is_format_tag<FormatTag> >, void>::type::value>::type*) [with Device = std::__cxx11::basic_stringstream<char>; Image = boost::gil::image<boost::gil::pixel<unsigned char, boost::gil::layout<boost::mp11::mp_list<boost::gil::red_t, boost::gil::green_t, boost::gil::blue_t> > >, false, std::allocator<unsigned char> >; FormatTag = boost::gil::png_tag; typename std::enable_if<typename boost::mp11::detail::mp_and_impl<boost::mp11::mp_list<boost::gil::detail::is_read_device<FormatTag, Device, void>, boost::gil::is_format_tag<FormatTag> >, void>::type::value>::type = void; typename boost::mp11::detail::mp_and_impl<boost::mp11::mp_list<boost::gil::detail::is_read_device<FormatTag, Device, void>, boost::gil::is_format_tag<FormatTag> >, void>::type = std::integral_constant<bool, true>]’ test_gcc11_gil.cc:11:30: required from here /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/io/make_reader.hpp:193:30: error: no matching function for call to ‘boost::gil::image_read_settings<boost::gil::png_tag>::image_read_settings()’ 193 | return make_reader(file, image_read_settings<FormatTag>(), cc); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In file included from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/read.hpp:13, from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png.hpp:11, from test_gcc11_gil.cc:3: /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:718:5: note: candidate: ‘boost::gil::image_read_settings<boost::gil::png_tag>::image_read_settings(const point_t&, const point_t&)’ 718 | image_read_settings( const point_t& top_left | ^~~~~~~~~~~~~~~~~~~ /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:718:5: note: candidate expects 2 arguments, 0 provided /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:707:8: note: candidate: ‘constexpr boost::gil::image_read_settings<boost::gil::png_tag>::image_read_settings(const boost::gil::image_read_settings<boost::gil::png_tag>&)’ 707 | struct image_read_settings< png_tag > : public image_read_settings_base | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:707:8: note: candidate expects 1 argument, 0 provided /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:707:8: note: candidate: ‘constexpr boost::gil::image_read_settings<boost::gil::png_tag>::image_read_settings(boost::gil::image_read_settings<boost::gil::png_tag>&&)’ /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:707:8: note: candidate expects 1 argument, 0 provided Only gcc 11 will fail with '-std=c++20', gcc9 and gcc 10 worked fine. I guess that gcc11 has implemented more c++20 features than gcc9 and gcc10. Since the boost project updates more quickly than gcc, I hope this issue might be fixed in the next boost version. Thanks, Qiang Ren

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Dimension conversion for free?
by KL 08 Jan '22

08 Jan '22

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TypeTraits
by Gero Peterhoff 27 Dec '21

27 Dec '21

Hello John, Some time ago I asked whether further type traits would be included in boost. Unfortunately that somehow fizzled out. Because based on this, many useful functions and classes can first be defined that behave correctly. But the problems are much deeper and I would like to show a solution here. 1) For some types there are feature-tesing-macros (e.g. __cpp_char8_t, __cpp_unicode_characters), but not for most. So this is incomplete. So we need this (plus the __cpp_lib-macros): - __cpp_char8/16/32_t, __cpp charw_t, __cpp_char_t - __cpp_int8/16/32/64/128_t - __cpp_float16/32/64/80/128_t, __cpp_float16b_t - __cpp_bool_t 2) Building on this, we can then query, e.g. struct has_float80: bool_constant < #if defined (__cpp_float80_t) true #else false #endif > {}; template <typename Type> struct is_float80: bool_constant < #if defined (__cpp_float80_t) is_same_v<Type, float80> #else false #endif > {}; This has to be done for all types. 3) Then we can further classify; plus is_X_v and concepts: character: template <typename Type> struct is_character: bool_constant < #if defined (__cpp_char32_t) is_same_v<Type, char32_t> || #elif defined (__cpp_char16_t) is_same_v<Type, char16_t> || #elif defined (__cpp_char8_t) is_same_v<Type, char8_t> || #elif defined (__cpp_charw_t) is_same_v<Type, wchar_t> || #endif is_same_v<Type, char> > {}; template <typename Type> struct is_unsigned_character: bool_constant < is_unsigned_v<Type> && character_v<Type> > {}; template <typename Type> is_signed_character: bool_constant < is_signed_v<Type> && character_v<Type> > {}; float: template <typename Type> struct is_floating_point: bool_constant < #if defined (__cpp_float128_t) is_same_v<Type, float128_t> || #elif defined (__cpp_float80_t) is_same_v<Type, float80_t> || #elif defined (__cpp_float64_t) is_same_v<Type, float64_t> || #elif defined (__cpp_float32_t) is_same_v<Type, float32_t> || #elif defined (__cpp_float16b_t) is_same_v<Type, float16b_t> || #elif defined (__cpp_float16_t) is_same_v<Type, float16_t> || #endif false > {}; integer: template <typename Type> struct is_unsigned_integer: bool_constant < #if defined (__cpp_int128_t) is_same_v<Type, uint128_t> || #elif defined (__cpp_int64_t) is_same_v<Type, uint64_t> || #elif defined (__cpp_int32_t) is_same_v<Type, uint32_t> || #elif defined (__cpp_int16_t) is_same_v<Type, uint16_t> || #elif defined (__cpp_int8_t) is_same_v<Type, uint8_t> || #endif false > {}; template <typename Type> struct is_signed_integer: bool_constant < #if defined (__cpp_int128_t) is_same_v<Type, int128_t> || #elif defined (__cpp_int64_t) is_same_v<Type, int64_t> || #elif defined (__cpp_int32_t) is_same_v<Type, int32_t> || #elif defined (__cpp_int16_t) is_same_v<Type, int16_t> || #elif defined (__cpp_int8_t) is_same_v<Type, int8_t> || #endif false > {}; template <typename Type> struct is_integer: bool_constant < is_unsigned_integer_v<Type> || is_signed_integer_v<Type> > {}; logic: template <typename Type> struct is_logic: bool_constant < is_same_v<Type, bool> > {}; With that we would have created the basics to be able to continue working properly at all. 4) 3 more steps to make things easier #define bitsof(ARG) (size_t(sizeof(ARG) * CHAR_BIT)) Like std::numbers with std::strings with various constantans namespace strings { constexpr static auto empty = ""; constexpr static auto nullptr = "nullptr"; constexpr static auto Void = "void"; constexpr static auto True = "true"; constexpr static auto False = "false"; constexpr static auto indeterminate = "indeterminate"; constexpr static auto overdeterminate = "overdeterminate"; constexpr static auto underdeterminate = "underdeterminate"; constexpr static auto bin = "bin"; constexpr static auto oct = "oct"; constexpr static auto dec = "dec"; constexpr static auto hex = "hex"; constexpr static auto literal_bin = "0b"; constexpr static auto literal_oct = "0o"; constexpr static auto literal_dec = "0d"; constexpr static auto literal_hex = "0x"; } and more and for streams so that you don't have to fumble with the flags namespace detail { using format_flags_t = typename std::ios_base::fmtflags; static inline constexpr format_flags_t defaultfloat = format_flags_t{}, hexfloat = std::ios_base::fixed | std::ios_base::scientific; inline format_flags_t get_flags (const std::ios_base & stream, const format_flags_t & fieldmask) noexcept { return stream.flags () & fieldmask; } } // detail inline bool is_boolalpha (const std::ios_base & stream) noexcept {return (stream.flags () & stream.boolalpha) == stream.boolalpha; } inline bool is_showbase (const std::ios_base & stream) noexcept {return (stream.flags () & stream.showbase) == stream.showbase; } inline bool is_showpoint (const std::ios_base & stream) noexcept {return (stream.flags () & stream.showpoint) == stream.showpoint; } inline bool is_skip (const std::ios_base & stream) noexcept {return (stream.flags () & stream.skipws) == stream.skipws; } inline bool is_uppercase (const std::ios_base & stream) noexcept {return (stream.flags () & stream.uppercase) == stream.uppercase; } inline bool is_lowercase (const std::ios_base & stream) noexcept {return! is_uppercase (stream); } inline bool is_float_bin (const std::ios_base & stream) noexcept {return false; } inline bool is_float_hex (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.floatfield) == detail::hexfloat; } inline bool is_float_fixed (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.floatfield) == stream.fixed; } inline bool is_float_default (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.floatfield) == detail::defaultfloat; } inline bool is_float_scientific (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.floatfield) == stream.scientific; } inline bool is_integer_bin (const std::ios_base & stream) noexcept {return false; } inline bool is_integer_oct (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.basefield) == stream.oct; } inline bool is_integer_dec (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.basefield) == stream.dec; } inline bool is_integer_hex (const std::ios_base & stream) noexcept {return detail::get_flags (stream, stream.basefield) == stream.hex; } 5) And now we can finally get correctly working functions, e.g. template <integer Type, unsigned_integer Bits> inline constexpr Type shl(const Type& arg, const Bits& bits) noexcept { using unsigned_type = make_unsigned_t<Type>; const type res {Type(arg << unsigned_type(bits))}; return (bits < bitsof(Type)) ? res : Type{0}; } template <integer Type, unsigned_integer Bits> inline constexpr Type shr(const Type& arg, const Bits& bits) noexcept { using unsigned_type = make_unsigned_t<Type>; const type ovl {is_signed_integer_v<Type> ? ((arg < Type{0})? Type(-1) : Type{0}) : Type{0}}, res {Type(arg >> unsigned_type(bits))}; return (bits < bitsof(Type)) ? res : ovl; } and classes, e.g. constexpr bool2/3/4 with template <> struct is_logic<bool4>: true_type {}; template <> struct is_logic<bool3>: true_type {}; template <> struct is_logic<bool2>: true_type {}; (I am happy to send it to you, because boost::tribool does not meet the requirements). PS: I could have used the days multi-array/multi-index; but that's done because all of these libs are not constexpr. Will these be updated again? thx Gero

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