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Subject: [Boost-users] boost::units - converting from one derived_dimension to another across systems (imperial to metric)
From: Matt Vinson (matt.vinson_at_[hidden])
Date: 2018-11-20 04:09:20

 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_at_[hidden] <boost-users-request_at_[hidden]> wrote:
 
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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_at_[hidden]>
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] boost::units - converting from one
    derived_dimension to another across systems (imperial to metric)
Message-ID:
    <CAHhxtD6A9Jwhv5amKnTa1bmNkD0U4_LGre8ySKFfQXK7w62oEQ_at_[hidden]>
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_at_[hidden]>
To: degski <degski_at_[hidden]>, boost-users_at_[hidden]
Subject: Re: [Boost-users] Fwd: Boost::Filesystem - How to iterate,
    through the whole drive
Message-ID: <d13622b0-9a68-d109-c26e-b60e3a5c45c8_at_[hidden]>
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_at_[hidden] <mailto:boost-users_at_[hidden]>> wrote:
>
>
>
>    ---------- Forwarded message ---------
>    From: *Richard Z?vodn?* <zavodnyrichard_at_[hidden]
>    <mailto:zavodnyrichard_at_[hidden]>>
>    Date: Sat, Nov 17, 2018, 3:59 PM
>    Subject: Boost::Filesystem - How to iterate, through the whole drive
>    To: <boost-users_at_[hidden] <mailto:boost-users_at_[hidden]>>
>
>
>    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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Message: 3
Date: Mon, 19 Nov 2018 11:36:01 -0700
From: Steven Watanabe <watanabesj_at_[hidden]>
To: Matt Vinson via Boost-users <boost-users_at_[hidden]>
Subject: Re: [Boost-users] boost::units - converting from one
    derived_dimension to another across systems (imperial to metric)
Message-ID: <2b2343b9-a6d1-9409-896a-bcb3e153a0a0_at_[hidden]>
Content-Type: text/plain; charset=utf-8
AMDG
On 11/16/2018 05:27 AM, Matt Vinson via Boost-users wrote:
> Thanks for input...Ok, I have errors creating a 'lineal force unit'.
> In our branch of engineering, we have kips****/ft, kips/in, lbs/foot, lbs/in, kN/meter, Kn/cm, KN/mm, N/meter, N/cm, N/mm, Metric Ton/meter, Metric Ton/cm, Metric Ton/mm, KiloGram/meter $, KiloGram/cm, KiloGram/mm, etc....All these units* are loosing force divided by length.
> After all the appreciated input in this thread, I thought I'd try this but it does not compile*** probably because force is "L M T^-2" and length is "L" which is not correct:?? ???? //Lineal Force
> ?? ???? typedef boost::units::derived_dimension<
> ?? ??? ??? ?boost::units::force_dimension, 1,
> ?? ??? ??? ?boost::units::length_dimension, -1
> ?? ??? ?>::type lineal_force_dimension;
> 
derived_dimension works with the base_dimensions not a dimension list.
Use either:
boost::units::derived_dimension<
  boost::units::mass_base_dimension, 1,
  boost::units::time_base_dimension, -2>::type
or
boost::mpl::divides<
  boost::units::force_dimension,
  boost::units::length_dimension>::type
> How can I use Boost.Units to convert one force/length to another force/length: say, lb/in to, say, kg/m?
> *not Boost.Units**, the units in the engineering math equation**A set of base units raised to rational exponents, e.g. m^1, kg^1, m^1/s^2. 
> *** ...\boost_1_68_0\boost\mpl\aux_\preprocessed\plain\less.hpp(20): error C2039: 'value': is not a member of 'boost::units::detail::dimension_list_tag'
> <snip>>
In Christ,
Steven Watanabe
------------------------------
Message: 4
Date: Mon, 19 Nov 2018 10:44:34 -0800
From: Marshall Clow <mclow.lists_at_[hidden]>
To: Boost users list <boost-users_at_[hidden]>
Subject: Re: [Boost-users] [release] Boost 1.69.0 Beta 1
Message-ID:
    <CAMBqOsgUjiDX+crLYDarqVtFrsnMZkSG+NC_DANh-D6npugbrg_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
On Sun, Nov 18, 2018 at 6:55 PM Michael Powell via Boost-users <
boost-users_at_[hidden]> wrote:
> On Sun, Nov 18, 2018 at 9:29 PM Marshall Clow via Boost-users
> <boost-users_at_[hidden]> wrote:
> >
> > Boost release 1.69.0 beta 1 is now available at:
> >    <https://dl.bintray.com/boostorg/beta/1.69.0.beta1/source/>
> >
> > The SHA256 checksums are as follows:
> >
> > ee0ecd7d31f58474c1e0210089c9e66bd878d4d1e7436ac511e359aa4a9d3e86
> ./boost_1_69_0_b1.7z
> > 3e25c46f2171799caabbeb419ba7859fffb62208f3a1c80798713377ab07af0e
> ./boost_1_69_0_b1.tar.bz2
> > 71f4b57175058af1b8c320971cf29226e5a652931a679f7e1c086655147ecafb
> ./boost_1_69_0_b1.tar.gz
> > ec9ef7d2c9f0d41f560769e67bc7ff207cc999243a7dd6c3f6bcfbdbf0827a7b
> ./boost_1_69_0_b1.zip
> >
> > For details of what's in the release, see <
> https://www.boost.org/users/history/version_1_69_0.html>.
> >
> > Please download the beta, give it a try, and report any problems you
> encounter.
>
> I'm confused. We just had a round of b1/rc1-3, didn't we?
>
Right. We had three "release candidates" beta1/rc1, rc2, and rc3.
This is the actual beta release - it is the same as RC3.
-- Marshall
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