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Interprocess: limited boost::any in shared memory
by Ferguson, Neil D CTR (US) 21 Nov '18

21 Nov '18

Sirs and madams, I hope to use boost interprocess shared memory to pass complex and dynamic data structures between processes on a host efficiently. The structures will be comprised only of simple primitives (int, float, etc.), interprocess basic_string, interprocess containers (vectors and maps), containers of containers, and (possible deal killer) boost::any. From the interprocess documentation, it _looks_ like the preceding is doable, aside from boost::any. The boost::any objects will themselves contain only primitives, basic_string, or interprocess vectors of unsigned char. So it _looks_ like the data held by the any should be okay. My question: does boost::any use pointers, references, or other constructs that preclude the class from working in shared memory? Thanks for your advice. Neil Ferguson

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boost::units - converting from one derived_dimension to another across systems (imperial to metric)
by Matt Vinson 21 Nov '18

21 Nov '18

Michael Powell: A) I hope to get Boost.Units to convert all these for me. I am replacing my own unit conversion classes with Boost.Units so there are no masking certain details, magic numbers, etc! Fingers Crossed. B) Boost.Units looks promising. Good to hear it has strong support. I'll keep at it. Thanks!// Steven Watanabe: Got it! You've been very patient and awesome. Thank you, yet again.I updated to this because I do need mass for density conversions:typedef boost::units::make_system< boost::units::us::inch_base_unit, boost::units::us::pound_base_unit, boost::units::us::pound_force_base_unit >::type ip_system; Any issues you see with boost::units::us::pound_base_unit for mass && boost::units::us::pound_force_base_unit for force? If I don't hear from you, I'll presume it's okay. My density unit testing* still passed after adding boost::units::us::pound_force_base_unit so I don't think there are issues. *each of these are converted to the other. enum class DENSITY : char { K_FT3 = 0, K_IN3 = 1, LB_FT3 = 2, LB_IN3 = 3, MT_M3 = 4, MT_CM3 = 5, MT_MM3 = 6, KG_M3 = 7, KG_CM3 = 8, KG_MM3 = 9, LAST = 10 }; On Tuesday, November 20, 2018, 9:09:45 PM CST, boost-users-request(a)lists.boost.org <boost-users-request(a)lists.boost.org> wrote: Send Boost-users mailing list submissions to boost-users(a)lists.boost.org To subscribe or unsubscribe via the World Wide Web, visit https://lists.boost.org/mailman/listinfo.cgi/boost-users or, via email, send a message with subject or body 'help' to boost-users-request(a)lists.boost.org You can reach the person managing the list at boost-users-owner(a)lists.boost.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Boost-users digest..." Today's Topics: 1. Re: boost::units - converting from one derived_dimension to another across systems (imperial to metric) (Michael Powell) 2. Re: Program Options documentation is anaemic (Gavin Lambert) 3. Re: boost::units - converting from one derived_dimension to another across systems (imperial to metric) (Steven Watanabe) 4. Re: Enquiry on boost.geometry and intersection() (Adam Wulkiewicz) ---------------------------------------------------------------------- Message: 1 Date: Tue, 20 Nov 2018 20:55:19 -0500 From: Michael Powell <mwpowellhtx(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] boost::units - converting from one derived_dimension to another across systems (imperial to metric) Message-ID: <CAMEoF_GFTg_Fx4haDdb2i65fEaOB_hnG8QmrgshMSG5-0XT5mQ(a)mail.gmail.com> Content-Type: text/plain; charset="UTF-8" On Tue, Nov 20, 2018 at 8:47 PM Matt Vinson via Boost-users <boost-users(a)lists.boost.org> wrote: > > degski: I do not think am making the "nauseam" mistake. My issue is using Boost.Units correctly which I concede is difficult for me but I am reading the docs and trying to get it. > In our field of engineering, we use Kg as a force; not a mass. (We also use pound as a force; not a mass - for your "UK's Weights and Measures Act 1963" counterpart). That said, I should not have made the mistake of using Kg as a force in Boost.Units, it's true. Shame on me. > My task is to convert between lineal forces: k/ft, k/in, lb/ft, lb/in, kN/m, kN/cm, kN/m, N/m, N/cm, N/m, Metric ton/m, Metric ton/cm, Metric ton/mm, Kg/m, Kg/cm, Kg/mm. These are all force/length. Coming from an energy oil and gas background applying Boost.Units, that's a difficult conversation to have especially when "units" are used, but in fact are masking certain details, magic numbers, etc, confounding their dimensions. > Steven Watanabe: Thank you, again. > #1: I was not trying to say it's wrong; sorry. Just that I did not see 'length' and opted for the one that did. The unit's are correct, as you say. > #2: This is an error to start with Kg(force)/meter. I can start with N/meter. I've changed this variable name to newton_per_meter and the conversion factors. I can tell you this much; once you get reasonably proficient with Boost.Units, there is a strong compiler confidence in correctness once you have your dimensions, units, etc, meshing well together. By that I mean, in truth, compile time confidence. The compiler / Boost.Units will tell you when you have it wrong, and it will compile when you have it correct. That's a major plus in my book. Cheers, best of luck! > *.h----------------------------------------------------- > > namespace dimensional_analysis { > > typedef boost::units::length_base_dimension::dimension_type length_dimension; > > typedef boost::units::mass_base_dimension::dimension_type mass_dimension; > > typedef boost::units::make_system<boost::units::us::inch_base_unit,boost::units::us::pound_base_unit>::type ip_system; > > namespace lineal_force { > > typedef boost::mpl::divides<boost::units::force_dimension,boost::units::length_dimension>::type lineal_force_dimension; > > namespace imperial { > > //////////////// > > ////lb/in, right? > > ////boost::units::force_dimension = pound > > ////boost::units::length_dimension = in > > //////////////// > > typedef boost::units::unit<lineal_force_dimension,lengths::ip_system> lineal_force_unit; > > } > > namespace si { > > //////////////// > > ////N/m, right? > > ////boost::units::force_dimension = newton > > ////boost::units::length_dimension = meter > > //////////////// > > typedef boost::units::unit<lineal_force_dimension,boost::units::si::system> lineal_force_unit; > > } > > }//lineal_force > > }//dimensional_analysis > > *.cpp----------------------------------------------------- > > //Imperial lb/in to SI N/m > > BOOST_UNITS_DEFINE_CONVERSION_FACTOR( > > dimensional_analysis::lineal_force::imperial::lineal_force_unit, > > dimensional_analysis::lineal_force::si::lineal_force_unit, > > double, > > 175.1268369864); // exact conversion > > BOOST_UNITS_DEFAULT_CONVERSION( > > dimensional_analysis::lineal_force::imperial::lineal_force_unit, > > dimensional_analysis::lineal_force::si::lineal_force_unit); > > //SI N/m to Imperial lb/in > > BOOST_UNITS_DEFINE_CONVERSION_FACTOR( > > dimensional_analysis::lineal_force::si::lineal_force_unit, > > dimensional_analysis::lineal_force::imperial::lineal_force_unit, > > double, > > 0.1837185501); // exact conversion > > BOOST_UNITS_DEFAULT_CONVERSION( > > dimensional_analysis::lineal_force::si::lineal_force_unit, > > dimensional_analysis::lineal_force::imperial::lineal_force_unit); > > //Imperial to SI. This should convert lb/in to N/m and return 175.1268369864 (N/m) > > //But it does not. Its converting lb (mass) to Kg (mass), 0.454 > > const auto t2 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( > > 1.0 * dimensional_analysis::lineal_force::imperial::lineal_force_unit::unit_type()); > > //Again, Imperial to SI. This should convert lb/in to N/m and return 175.1268369864 (N/m) > > //But it does not. It returns lb (mass) to Kg (mass) > > const auto t3 = boost::units::conversion_factor( > > dimensional_analysis::lineal_force::imperial::lineal_force_unit::unit_type(), > > dimensional_analysis::lineal_force::si::lineal_force_unit::unit_type()); > > //SI to Imperial. This should convert N/m to lb/in and return 0.1837185501 (lb/in) > > //But it does not. Its converting Kg (mass) to lb (mass), 2.205 > > const auto t1 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( > > 1.0 * dimensional_analysis::lineal_force::si::lineal_force_unit::unit_type()); > > //So, I don?t know why the library is converting mass; I?ve tuned it to use boost::units::force_dimension/boost::units::length_dimension > > //I am doing something wrong where the library is not using force/length. > > //Below does work, mainly. > > //This is convert Si to SI and return value of 1.0 is correct. > > const auto t4 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( > > 1.0 * boost::units::si::newton / boost::units::si::meter); > > //This convert lb/in to SI and return value is 175.1268369864 is correct. > > const auto t5 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( > > 1.0 * boost::units::us::pound_force_base_unit::unit_type() / boost::units::us::inch_base_unit::unit_type()); > > //This converts lb/in to lb/in and return value is of 1.0 is correct. > > const auto t6 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( > > 1.0 * boost::units::us::pound_force_base_unit::unit_type() / boost::units::us::inch_base_unit::unit_type()); > > //This is 2.205 and not correct. > > //It?s not converting SI-force/length to Imperial-force/length > > //Its converting Kg (mass) to lb (mass), 2.205 > > const auto t7 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( > > 1.0 * boost::units::si::newton / boost::units::si::meter); > > //What have I done wrong? > > //Any help is appreciated. > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > https://lists.boost.org/mailman/listinfo.cgi/boost-users ------------------------------ Message: 2 Date: Wed, 21 Nov 2018 15:55:35 +1300 From: Gavin Lambert <boost(a)mirality.co.nz> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Program Options documentation is anaemic Message-ID: <3ab79a24-e6ff-e311-1d12-adbe5646a123(a)mirality.co.nz> Content-Type: text/plain; charset=utf-8; format=flowed On 20/11/2018 23:03, David Demelier wrote: > Reading the type_value documentation from Boost Program options feels like: > > ??? typed_value * composing(); > ??? Specifies that the value is composing. See the 'is_composing' > method for explanation. > > And the documentation of is_composing: > > ??? bool is_composing() const; > > Not sure if I know more what this function is supposed to do now. I agree that this seems somewhat unhelpful. FWIW a quick look elsewhere found https://www.boost.org/doc/libs/1_68_0/doc/html/program_options/tutorial.htm… which describes that option in more detail -- specifically that it's whether repeated parameters are merged or just replace the older value. > Also, I think this module/documentation should take a s/method/function/g. "Method" is the more common name for a method within a class. ------------------------------ Message: 3 Date: Tue, 20 Nov 2018 19:58:27 -0700 From: Steven Watanabe <watanabesj(a)gmail.com> To: Matt Vinson via Boost-users <boost-users(a)lists.boost.org> Cc: matt.vinson(a)sbcglobal.net Subject: Re: [Boost-users] boost::units - converting from one derived_dimension to another across systems (imperial to metric) Message-ID: <4f601999-f01c-0535-37a3-15e6e21d8331(a)gmail.com> Content-Type: text/plain; charset=utf-8 AMDG On 11/20/2018 06:46 PM, Matt Vinson via Boost-users wrote: > <snip> > <some reformatting to reduce line wrapping> > *.h----------------------------------------------------- > > namespace dimensional_analysis { > > ????typedef length_base_dimension::dimension_type length_dimension; > ????typedef mass_base_dimension::dimension_type mass_dimension; > > typedef make_system<inch_base_unit,pound_base_unit>::type ip_system; > This should be pound_force_base_unit. > ? namespace lineal_force { > ??? typedef mpl::divides<force_dimension,length_dimension>::type lineal_force_dimension;?????????? > > ??? namespace imperial { > > ????? //////////////// > ????? ////lb/in, right? > > ////boost::units::force_dimension =pound > ////boost::units::length_dimension = in > ????? //////////////// > ????? typedef unit<lineal_force_dimension,lengths::ip_system> lineal_force_unit; This unit is nonsensical because the ip_system as written is unable to represent the lineal_force_dimension. That this doesn't give a hard compiler error is a bug in the library. Once you fix ip_system, the conversions should be right. > ??? } > ??? namespace si { > ??? //////////////// > ??? ////N/m, right? > Yep. > ////boost::units::force_dimension = newton > ////boost::units::length_dimension = meter > ????? //////////////// > ????? typedef unit<lineal_force_dimension,si::system> lineal_force_unit; > ??? } > ? }//lineal_force > }//dimensional_analysis > > *.cpp----------------------------------------------------- > > //Imperiallb/in to SI N/m > The following conversion definitions are unnecessary and have no effect: > BOOST_UNITS_DEFINE_CONVERSION_FACTOR( > dimensional_analysis::lineal_force::imperial::lineal_force_unit, > dimensional_analysis::lineal_force::si::lineal_force_unit, > double, > 175.1268369864); // exact conversion > > BOOST_UNITS_DEFAULT_CONVERSION( > dimensional_analysis::lineal_force::imperial::lineal_force_unit, > dimensional_analysis::lineal_force::si::lineal_force_unit); > > //SI N/mto Imperial lb/in > > BOOST_UNITS_DEFINE_CONVERSION_FACTOR( > dimensional_analysis::lineal_force::si::lineal_force_unit, > dimensional_analysis::lineal_force::imperial::lineal_force_unit, > double, > 0.1837185501); // exact conversion > > BOOST_UNITS_DEFAULT_CONVERSION( > dimensional_analysis::lineal_force::si::lineal_force_unit, > dimensional_analysis::lineal_force::imperial::lineal_force_unit); > > <snip> > In Christ, Steven Watanabe ------------------------------ Message: 4 Date: Wed, 21 Nov 2018 04:09:11 +0100 From: Adam Wulkiewicz <adam.wulkiewicz(a)gmail.com> To: Zhang Qun <zhangq.rhy(a)gmail.com> Cc: boost-users(a)lists.boost.org Subject: Re: [Boost-users] Enquiry on boost.geometry and intersection() Message-ID: <9d3e335d-df1a-7627-af4f-a9d3fd8c22ff(a)gmail.com> Content-Type: text/plain; charset="utf-8"; Format="flowed" Please do not top-post. Zhang Qun?wrote: > Hi Adam > I think I have figured it out. Because of the precision, the two > polygons are not the same. > > That also explains that why sometimes the intersection() gives me two > intersection points looking "exactly" the same but if you look at the > double precision, they are actually two different points. In reality, > these two points can be safely considered the same point. I can solve > this by comparing the two points distance. However, sometimes also > because of the precision, the intersection() does not even give me any > intersection points especially when the line is right across the > vertex of the polygon. How do I solve this kind of problem? Could you paste the WKTs of geometries (with sufficient precision) [1] and say what do you get and what do you expect? [1] e.g. std::cout << std::setprecision(20) << bg::wkt(polygon) << std::endl; Adam

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Enquiry on boost.geometry and intersection()
by Zhang Qun 21 Nov '18

21 Nov '18

Hi guys, first-time post here. Hello to everyone. I'm using boost.geometry to implement a project. I need to calculate the intersection between a line and a polygon. I know there is no infinite line concept in boost.geometry. So I try to use the segment to intersect with a polygon, however, it seems not supported yet. Is there any other workaround that I can implement the intersection between a line and a polygon? The line is like y=mx+b or ax + by + c = 0. Thanks. Ethan

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boost::units - converting from one derived_dimension to another across systems (imperial to metric)
by Matt Vinson 21 Nov '18

21 Nov '18

degski: I do not think am making the "nauseam" mistake. My issue is using Boost.Units correctly which I concede is difficult for me but I am reading the docs and trying to get it. In our field of engineering, we use Kg as a force; not a mass. (We also use pound as a force; not a mass - for your "UK's Weights and Measures Act 1963" counterpart). That said, I should not have made the mistake of using Kg as a force in Boost.Units, it's true. Shame on me. My task is to convert between lineal forces: k/ft, k/in, lb/ft, lb/in, kN/m, kN/cm, kN/m, N/m, N/cm, N/m, Metric ton/m, Metric ton/cm, Metric ton/mm, Kg/m, Kg/cm, Kg/mm. These are all force/length. Steven Watanabe: Thank you, again.#1: I was not trying to say it's wrong; sorry. Just that I did not see 'length' and opted for the one that did. The unit's are correct, as you say. #2: This is an error to start with Kg(force)/meter. I can start with N/meter. I've changed this variable name to newton_per_meter and the conversion factors. *.h----------------------------------------------------- namespace dimensional_analysis{ typedef boost::units::length_base_dimension::dimension_type length_dimension; typedef boost::units::mass_base_dimension::dimension_type mass_dimension; typedef boost::units::make_system<boost::units::us::inch_base_unit,boost::units::us::pound_base_unit>::type ip_system; namespace lineal_force { typedef boost::mpl::divides<boost::units::force_dimension,boost::units::length_dimension>::type lineal_force_dimension; namespace imperial { //////////////// ////lb/in, right? ////boost::units::force_dimension =pound ////boost::units::length_dimension = in //////////////// typedef boost::units::unit<lineal_force_dimension,lengths::ip_system> lineal_force_unit; } namespace si { //////////////// ////N/m, right? ////boost::units::force_dimension = newton ////boost::units::length_dimension = meter //////////////// typedef boost::units::unit<lineal_force_dimension,boost::units::si::system> lineal_force_unit; } }//lineal_force }//dimensional_analysis *.cpp----------------------------------------------------- //Imperiallb/in to SI N/m BOOST_UNITS_DEFINE_CONVERSION_FACTOR( dimensional_analysis::lineal_force::imperial::lineal_force_unit, dimensional_analysis::lineal_force::si::lineal_force_unit, double, 175.1268369864); // exact conversion BOOST_UNITS_DEFAULT_CONVERSION( dimensional_analysis::lineal_force::imperial::lineal_force_unit, dimensional_analysis::lineal_force::si::lineal_force_unit); //SI N/mto Imperial lb/in BOOST_UNITS_DEFINE_CONVERSION_FACTOR( dimensional_analysis::lineal_force::si::lineal_force_unit, dimensional_analysis::lineal_force::imperial::lineal_force_unit, double, 0.1837185501); // exact conversion BOOST_UNITS_DEFAULT_CONVERSION( dimensional_analysis::lineal_force::si::lineal_force_unit, dimensional_analysis::lineal_force::imperial::lineal_force_unit); //Imperialto SI. This should convert lb/in to N/m andreturn 175.1268369864(N/m) //But itdoes not. Its converting lb (mass) to Kg(mass), 0.454 const auto t2 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( 1.0 *dimensional_analysis::lineal_force::imperial::lineal_force_unit::unit_type()); //Again, Imperial to SI. This should convert lb/in to N/m and return 175.1268369864 (N/m) //But itdoes not. It returns lb (mass) to Kg(mass) const auto t3 = boost::units::conversion_factor( dimensional_analysis::lineal_force::imperial::lineal_force_unit::unit_type(), dimensional_analysis::lineal_force::si::lineal_force_unit::unit_type()); //SI toImperial. This should convert N/m tolb/in and return 0.1837185501 (lb/in) //But itdoes not. Its converting Kg (mass) to lb(mass), 2.205 const auto t1 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( 1.0 *dimensional_analysis::lineal_force::si::lineal_force_unit::unit_type()); //So, I don’t know whythe library is converting mass; I’ve tuned it to use boost::units::force_dimension/boost::units::length_dimension //I am doing something wrongwhere the library is not using force/length. //Below does work, mainly. //This isconvert Si to SI and return value of 1.0 is correct. const auto t4 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( 1.0 *boost::units::si::newton / boost::units::si::meter); //This convert lb/in to SI and return value is 175.1268369864 is correct. const auto t5 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( 1.0 * boost::units::us::pound_force_base_unit::unit_type() / boost::units::us::inch_base_unit::unit_type()); //This converts lb/in to lb/in and return value is of 1.0 is correct. const auto t6 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( 1.0 * boost::units::us::pound_force_base_unit::unit_type() / boost::units::us::inch_base_unit::unit_type()); //This is2.205 and not correct. //It’s notconverting SI-force/length to Imperial-force/length //Itsconverting Kg (mass) to lb (mass), 2.205 const auto t7 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( 1.0 * boost::units::si::newton /boost::units::si::meter); //What have I done wrong? //Any help is appreciated.

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Program Options documentation is anaemic
by David Demelier 21 Nov '18

21 Nov '18

Hello, Reading the type_value documentation from Boost Program options feels like: typed_value * composing(); Specifies that the value is composing. See the 'is_composing' method for explanation. And the documentation of is_composing: bool is_composing() const; Not sure if I know more what this function is supposed to do now. Also, I think this module/documentation should take a s/method/function/g. What's your thoughts on this? Regards, -- David

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[Spirit] uint_parser inconsistent results
by Michael Powell 20 Nov '18

20 Nov '18

Hello, I am trying to figure out why the uint_parser yields what looks like raw characters in one instance, yet in another instance yields the original given phrase. What do I mean by that? I have a string-literal rule, subset of the Google protobuf v2 grammar, and the octal-escaped rule yields a raw character, but the "same" hex-escaped rule yields the given input string. Both rules are of type qi::rule<It, char()>. And the str_lit rule is qi::rule<It, std::string()>, basically. oct_esc %= '\\' >> uint_parser<unsigned char, 8, 3, 3>{}; hex_esc %= no_case["\\x"] >> uint_parser<unsigned char, 16, 2, 2>{}; char_val %= hex_esc | oct_esc | char_esc | ~char_("\0\n\\"); str_lit %= ("'" >> *(char_val - "'") >> "'") | ('"' >> *(char_val - '"') >> '"') ; struct escapes_t : qi::symbols<char, char> { escapes_t() { this->add("\\a", '\a') ("\\b", '\b') ("\\f", '\f') ("\\n", '\n') ("\\r", '\r') ("\\t", '\t') ("\\v", '\v') ("\\\\", '\\') ("\\'", '\'') ("\\\"", '"') ; } } char_esc; The only thing I can figure is that perhaps it has something to do with no-case having a secondary effect on the rule? I do not care which way it lands, per se, in either raw or original string, although landing in the raw, that is, unescaped, has some advantages, I suppose. However, it is a mystery to me how there are two different outcomes. Any thoughts? Suggestions? Thanks! Michael Powell

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questions about visibility/dlls under mingw
by Robert Ramey 20 Nov '18

20 Nov '18

MINGW is the platform which runs gcc compilers under winsoze. I include all the visibility attribute in the "right" places with serialization build and tests. This is looking like it's passing on all platforms EXCEPT MINGW. I think MINGW uses the windows attributes, but I'm wonder if our boost setup uses the gcc macros. This would explain the bahavior I'm getting now. But honestly I really have no idea. here's the link to the appveyor results: https://ci.appveyor.com/project/RobertRamey/serialization/builds/20309631 Perhaps this is a config issue? or I'm doing wrong? I'm loath to much with this just for this one platform. Robert Ramey

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Fwd: Boost::Filesystem - How to iterate, through the whole drive
by Richard Závodný 20 Nov '18

20 Nov '18

---------- Forwarded message --------- From: Richard Závodný <zavodnyrichard(a)gmail.com> Date: Sat, Nov 17, 2018, 3:59 PM Subject: Boost::Filesystem - How to iterate, through the whole drive To: <boost-users(a)lists.boost.org> Hey guys, I need iterate over all directories from starting path. If I start iterating from C:\some-dir it works very well, however if I try to iterate from C:\, it doesn't work. How can iterate through the whole drive? Thank you. Code is here: https://pastebin.com/mpsKJxH2 <https://pastebin.com/3J6FEMG5>. The problem I experience is commented right in the code section (line 1, 13 and 25).

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boost::units - converting from one derived_dimension to another across systems (imperial to metric)
by Matt Vinson 20 Nov '18

20 Nov '18

Eisuke Kawashima: Thank You. I'll have a look. When I saw Boost.Units did not have imperial and we had to create it ourselves, I thought: the US is s 5 trillion dollar market, most of those markets need programming, all are on imperial. Boost.Units needs imperial and programmers would find and use it. Steven Watanabe: Thank You. This solution doesn't seem correct as it does not consider "length".... boost::units::derived_dimension< boost::units::mass_base_dimension, 1, boost::units::time_base_dimension, -2>::typeI thought I'd at it (L M T^-2 L-1) but this didn't do well.: typedef boost::units::derived_dimension< boost::units::length_base_dimension, 1, boost::units::mass_base_dimension, 1, boost::units::time_base_dimension, -2, boost::units::length_base_dimension, -1 >::type lineal_force_dimension; So, I tried the " typedef boost::mpl::divides<...>" solution as it has force and length. I am closer, I hope. *.h------------------------------------------------------------------------------------------------------------------------------------------ namespace dimensional_analysis { typedef boost::units::length_base_dimension::dimension_type length_dimension; typedef boost::units::mass_base_dimension::dimension_type mass_dimension; typedef boost::units::make_system< boost::units::us::inch_base_unit, boost::units::us::pound_base_unit >::type ip_system; namespace lineal_force { typedef boost::mpl::divides< boost::units::force_dimension, boost::units::length_dimension>::type lineal_force_dimension; namespace imperial { typedef boost::units::unit< lineal_force_dimension, dimensional_analysis ::ip_system > lineal_force_unit; typedef boost::units::quantity<lineal_force_unit, double> pound_per_in_quantity; BOOST_UNITS_STATIC_CONSTANT(pound_per_inch, pound_per_in_quantity); } namespace si { typedef boost::units::unit< lineal_force_dimension, boost::units::si::system > lineal_force_unit; typedef boost::units::quantity<lineal_force_dimension, double> kg_per_meter_quantity; BOOST_UNITS_STATIC_CONSTANT(kg_per_meter, kg_per_meter_quantity); } }//lineal_force }//dimensional_analysis *.cpp------------------------------------------------------------------------------------------------------------------------------------------ BOOST_UNITS_DEFINE_CONVERSION_FACTOR(dimensional_analysis::lineal_force::imperial::lineal_force_unit, dimensional_analysis::lineal_force::si::lineal_force_unit, double, 17.858); // exact conversion BOOST_UNITS_DEFAULT_CONVERSION(dimensional_analysis::lineal_force::imperial::lineal_force_unit, dimensional_analysis::lineal_force::si::lineal_force_unit); BOOST_UNITS_DEFINE_CONVERSION_FACTOR(dimensional_analysis::lineal_force::si::lineal_force_unit, dimensional_analysis::lineal_force::imperial::lineal_force_unit, double, 0.0559974); // exact conversion BOOST_UNITS_DEFAULT_CONVERSION(dimensional_analysis::lineal_force::si::lineal_force_unit, dimensional_analysis::lineal_force::imperial::lineal_force_unit); //This is not converting force/length and is converting si -> imperial mass (only) = 110.2. Needs to consider force/length, =50*0.0559974 auto t1 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::imperial::lineal_force_unit>>( 50.0 * dimensional_analysis::lineal_force::si::lineal_force_unit::unit_type()); / This is not converting force/length and i sconverting imperial -> si mass (only) = 22.7. Needs to consider force/length, =50*17.858 auto t2 = static_cast<boost::units::quantity<dimensional_analysis::lineal_force::si::lineal_force_unit>>( 50.0 * dimensional_analysis::lineal_force::imperial::lineal_force_unit::unit_type()); //This is again only converting mass and needs to convert force/length const auto t3 = boost::units::conversion_factor( dimensional_analysis::lineal_force::imperial::lineal_force_unit::unit_type(), dimensional_analysis::lineal_force::si::lineal_force_unit::unit_type()); On Monday, November 19, 2018, 12:46:57 PM CST, boost-users-request(a)lists.boost.org <boost-users-request(a)lists.boost.org> wrote: Send Boost-users mailing list submissions to boost-users(a)lists.boost.org To subscribe or unsubscribe via the World Wide Web, visit https://lists.boost.org/mailman/listinfo.cgi/boost-users or, via email, send a message with subject or body 'help' to boost-users-request(a)lists.boost.org You can reach the person managing the list at boost-users-owner(a)lists.boost.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Boost-users digest..." Today's Topics: 1. Re: boost::units - converting from one derived_dimension to another across systems (imperial to metric) (Eisuke Kawashima) 2. Re: Fwd: Boost::Filesystem - How to iterate, through the whole drive (Richard Z?vodn?) 3. Re: boost::units - converting from one derived_dimension to another across systems (imperial to metric) (Steven Watanabe) 4. Re: [release] Boost 1.69.0 Beta 1 (Marshall Clow) ---------------------------------------------------------------------- Message: 1 Date: Tue, 20 Nov 2018 02:23:10 +0900 From: Eisuke Kawashima <e.kawaschima+boost(a)gmail.com> To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] boost::units - converting from one derived_dimension to another across systems (imperial to metric) Message-ID: <CAHhxtD6A9Jwhv5amKnTa1bmNkD0U4_LGre8ySKFfQXK7w62oEQ(a)mail.gmail.com> Content-Type: text/plain; charset="UTF-8" Hi list, > I am having trouble converting from one derived_dimension to another across systems (imperial to metric). I'd like to convert, say, lb/in to, say, kg/m. I thought I would do the following but get a compiler error #: > > *.h-------------------------------------------------------------------------------- > namespace dimensional_analysis { > namespace lineal_force { > //lb/in > typedef boost::units::derived_dimension< > boost::units::us::pound_force_base_unit, 1, > boost::units::us::inch_base_unit, -1 > >::type lb_per_inch_dimension; > typedef boost::units::unit< > lb_per_inch_dimension, > dimensional_analysis::lengths::ip_system > > lb_per_inch_unit; > typedef boost::units::quantity<lb_per_inch_unit, double> lb_per_inch_quantity; > BOOST_UNITS_STATIC_CONSTANT(lbpin, lb_per_inch_quantity); > //kg/m > typedef boost::units::derived_dimension< > boost::units::si::kilogram_base_unit, 1, > boost::units::si::meter_base_unit, -1 > >::type kg_per_meter_dimension; > typedef boost::units::unit< > kg_per_meter_dimension, > boost::units::si::system > > kg_per_meter_unit; > typedef boost::units::quantity<kg_per_meter_unit, double> kg_per_meter_unit_quantity; > BOOST_UNITS_STATIC_CONSTANT(kgpm, kg_per_meter_unit_quantity); > }//lineal_force > }//dimensional_analysis > > *.cp ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > //Do I need these? > BOOST_UNITS_DEFINE_CONVERSION_FACTOR(dimensional_analysis::lineal_force::kg_per_meter_unit, dimensional_analysis::lineal_force::lb_per_inch_unit, double, 0.0559974); // exact conversion > BOOST_UNITS_DEFAULT_CONVERSION(dimensional_analysis::lineal_force::kg_per_meter_unit, dimensional_analysis::lineal_force::lb_per_inch_unit); > > //This does not compile# > const auto conv_factor_try0 = conversion_factor(dimensional_analysis::lineal_force::kg_per_meter_unit::unit_type(), dimensional_analysis::lineal_force::lb_per_inch_unit::unit_type()); > > # *\boost_1_68_0\boost\units\detail\conversion_impl.hpp(340): error C2672: 'conversion_factor': no matching overloaded function found (compiling source file...*.cpp) > > Any help is appreciated I opened a PR (https://github.com/boostorg/units/pull/32) to address such a situation; the following code ```cpp #include <iostream> #include <boost/units/base_units/us/inch.hpp> #include <boost/units/base_units/us/pound_force.hpp> #include <boost/units/io.hpp> #include <boost/units/physical_dimensions.hpp> #include <boost/units/systems/si.hpp> int main() { auto force_us{1.0 * boost::units::us::pound_force}; auto length_us{1.0 * boost::units::us::inch}; boost::units::quantity<boost::units::si::force, double> force_si{force_us}; boost::units::quantity<boost::units::si::length, double> length_si{length_us}; std::cout << force_us << " = " << force_si << '\n'; std::cout << length_us << " = " << length_si << '\n'; std::cout << force_us / length_us << " = " << force_si / length_si << '\n'; return 0; } ``` will print ``` 1 lbf = 4.44822 m kg s^-2 1 in = 0.0254 m 1 lbf in^-1 = 175.127 kg s^-2 ``` Best -- Eisuke Kawashima ------------------------------ Message: 2 Date: Mon, 19 Nov 2018 19:24:58 +0100 From: Richard Z?vodn? <zavodnyrichard(a)gmail.com> To: degski <degski(a)gmail.com>, boost-users(a)lists.boost.org Subject: Re: [Boost-users] Fwd: Boost::Filesystem - How to iterate, through the whole drive Message-ID: <d13622b0-9a68-d109-c26e-b60e3a5c45c8(a)gmail.com> Content-Type: text/plain; charset="utf-8"; Format="flowed" I just wanna try it again here, maybe somebody will shop up who knows where is the problem as I unfortunately couldn't fix it with degski (but still, thank you for your time :)). His example (can be found below) doesn't work on my system. The problem is I can't start iteration from the drive root (for example E:\), because it will iterate only the directory above (E:\projects\boost\build) the directory that the executable is located in (the executable is located in E:\projects\boost\build\Debug). What is weird that if I move the executable to the different directory (let's say C:\Users\USER_NAME\Downloads) it will still iterate only the build directory. I tried to play with Visual Studio -> PROJECT_NAME -> Properties -> Debugging -> Working Directory, but without a success. According to degski he has the value of this entry set to $(ProjectDir) which is the same value as mine. Thank you. On 11/18/2018 9:04 AM, degski wrote: > On Sun, 18 Nov 2018 at 05:31, Richard Z?vodn? via Boost-users > <boost-users(a)lists.boost.org <mailto:boost-users@lists.boost.org>> wrote: > > > > ---------- Forwarded message --------- > From: *Richard Z?vodn?* <zavodnyrichard(a)gmail.com > <mailto:zavodnyrichard@gmail.com>> > Date: Sat, Nov 17, 2018, 3:59 PM > Subject: Boost::Filesystem - How to iterate, through the whole drive > To: <boost-users(a)lists.boost.org <mailto:boost-users@lists.boost.org>> > > > Hey guys, I need iterate over all directories from starting path. > If I start iterating from C:\some-dir it works very well, however > if I try to iterate from C:\, it doesn't work. How can iterate > through the whole drive? Thank you. > > > Code is here: https://pastebin.com/mpsKJxH2 > <https://pastebin.com/3J6FEMG5>. The problem I experience is > commented right in the code section (line 1, 13 and 25). > > > This works for me, either with boost-1.68 (not that I think that > matters) or the STL-VC-15.9.1 (/std:c++17): > > #include <iostream> > #include <boost/filesystem.hpp> > > namespace fs = boost::filesystem; > > int main ( ) { > ??? for ( auto & p : fs::recursive_directory_iterator ( "d:\\" ) ) { > ??????? std::cout << p.path ( ) << '\n'; > ??? } > } > > Note that: "The iteration order is unspecified, except that each > directory entry is visited only once." > > degski > -- > /*/*?*/If something cannot go on forever, it will stop" - Herbert Stein*/

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Making an ASIO asynchronous operation from flock()
by Cristian Morales Vega 20 Nov '18

20 Nov '18

So I need to flock (http://man7.org/linux/man-pages/man2/flock.2.html) something (pre-existing flock in other piece of software to interoperate with) and I though: "I think I'm actually starting to understand ASIO, let's make a proper ASIO asynchronous operation with flock". Long story short, I now know better: I will never get ASIO. So my main issues are with the background thread. According to https://www.boost.org/doc/libs/develop/doc/html/boost_asio/overview/core/th… "the threads ... must block all signals". OK, it makes sense, but... - I can make pthread_sigmask() the first thing once the std::thread starts executing. But, I can't really guarantee the thread will never receive a signal, can I? There is a small amount of time between the thread starting to be able to receive signals and pthread_sigmask() doing its job. Modifying the signal mask before the background thread is created (so also from the "not-background" thread) doesn't seem a lot better. - How do I cancel the asynchronous operation? flock() is blocking, not a lot I can do to unblock it. I could send a signal to the background thread, but... they must be blocked, so no. I can't join the thread while it's blocked in flock(). So... should it be detached? I could then maybe just destroy the std::thread, but I still need to call the handler with boost::asio::error::operation_aborted... So, my question: I'm making it more difficult than it is? There is some pattern I should be following which makes all this simple? See what I have below (sorry for the camel case) ------------------------------------------------------------------------------- #include <boost/asio.hpp> #include <boost/beast/core/bind_handler.hpp> #include <boost/system/error_code.hpp> #include <boost/system/system_error.hpp> #include <fcntl.h> #include <iostream> #include <sys/file.h> #include <sys/stat.h> #include <sys/types.h> #include <thread> namespace asio = boost::asio; using error_code = boost::system::error_code; using system_error = boost::system::system_error; class FLockablePosixDescriptor : public asio::posix::descriptor { public: enum class FlockType : int { SHARED = LOCK_SH, EXCLUSIVE = LOCK_EX }; using asio::posix::descriptor::descriptor; FLockablePosixDescriptor(FLockablePosixDescriptor &&) = default; FLockablePosixDescriptor &operator=(FLockablePosixDescriptor &&) = default; ~FLockablePosixDescriptor(); template <typename FLockToken> BOOST_ASIO_INITFN_RESULT_TYPE(FLockToken, void(error_code)) asyncFLock(FlockType type, FLockToken &&token); void cancel(); void cancel(error_code &ec); private: template <typename FLockHandler> void doFLock(int fd, FlockType type, FLockHandler &handler); asio::io_context mBackgroundContext{1}; std::thread mThread; }; FLockablePosixDescriptor::~FLockablePosixDescriptor() { mBackgroundContext.stop(); mThread.join(); } template <typename FLockToken> BOOST_ASIO_INITFN_RESULT_TYPE(FLockToken, void(error_code)) FLockablePosixDescriptor::asyncFLock(FlockType type, FLockToken &&token) { asio::async_completion<FLockToken, void(error_code)> init(token); mBackgroundContext.post([this, fd = native_handle(), type, handler = std::move(init.completion_handler), work = asio::make_work_guard(get_executor())] { doFLock(fd, type, handler); }); mThread = std::thread([this] { mBackgroundContext.run(); }); return init.result.get(); } template <typename FLockHandler> void FLockablePosixDescriptor::doFLock(int fd, FlockType type, FLockHandler &handler) { error_code ec; if (flock(fd, static_cast<int>(type)) == -1) { ec = error_code(errno, boost::system::system_category()); } asio::post(get_executor(), boost::beast::bind_handler(handler, ec)); } void FLockablePosixDescriptor::cancel() { error_code ec; cancel(ec); if (ec) { throw system_error(ec, "cancel"); } } void FLockablePosixDescriptor::cancel(error_code &ec) { // TODO: Cancel flock asio::posix::descriptor::cancel(ec); } int main() { boost::asio::io_context ioc; int fd = open("l", O_RDONLY); FLockablePosixDescriptor desc(ioc, fd); desc.asyncFLock(FLockablePosixDescriptor::FlockType::SHARED, [](const error_code &ec) { std::clog << "Done " << ec << std::endl; }); ioc.run(); } -------------------------------------------------------------------------------

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