[Boost-users] boost::units - converting from one derived_dimension to another across systems (imperial to metric)

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 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 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>( 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>( 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@lists.boost.org wrote: Send Boost-users mailing list submissions to     boost-users@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@lists.boost.org You can reach the person managing the list at     boost-users-owner@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 To: boost-users@lists.boost.org Subject: Re: [Boost-users] boost::units - converting from one     derived_dimension to another across systems (imperial to metric) Message-ID:     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_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_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 #include #include #include #include int main() {   auto force_us{1.0 * boost::units::us::pound_force};   auto length_us{1.0 * boost::units::us::inch};   boost::units::quantity force_si{force_us};   boost::units::quantity 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? To: degski , boost-users@lists.boost.org Subject: Re: [Boost-users] Fwd: Boost::Filesystem - How to iterate,     through the whole drive Message-ID: 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 mailto:boost-users@lists.boost.org> wrote:

    ---------- Forwarded message ---------     From: *Richard Z?vodn?* mailto:zavodnyrichard@gmail.com>     Date: Sat, Nov 17, 2018, 3:59 PM     Subject: Boost::Filesystem - How to iterate, through the whole drive     To: 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

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*/