我使用了这个approach来定义一个新的派生尺寸质量流,该质量流应该具有单位kg / s:

包括

#include <boost/units/io.hpp>
#include <boost/units/systems/si.hpp>
#include <boost/units/systems/si/io.hpp>
#include <boost/units/systems/si/prefixes.hpp>

namespace Units
{
  using namespace boost::units;

  namespace SI
  {
    using namespace boost::units::si;
  }

  template <class U> using Quantity = quantity<U>;

  typedef Quantity<SI::time> Time;
  typedef Quantity<SI::mass> Mass;

  typedef Units::derived_dimension<Units::mass_base_dimension, 1,
                                   Units::time_base_dimension, -1>::type MassFlowDimension;

  typedef Quantity<MassFlowDimension> MassFlowRate;

  BOOST_UNITS_STATIC_CONSTANT(kilogram_per_seconds, MassFlowRate);
}

我本以为从/转换为现有基本单位可以立即使用,但显然不是这样:
int main()
{
  // does work
  Units::MassFlowRate mass_flow = 1.0*(Units::kilogram_per_seconds);

  // does not work
  Units::MassFlowRate other_mass_flow = 1.0*(Units::SI::kilogram / Units::SI::second);

  // does not work either
  Units::Mass total_flow = mass_flow * (1.0*Units::SI::second);
}

我想使用派生的维度来定义集成到现有框架中的数量。我是否必须调用一些宏才能使其转换为现有单元或从现有单元转换为宏?

编辑:错误消息如下:
main.cc:39:44: error: conversion from ‘boost::units::multiply_typeof_helper<double, boost::units::unit<boost::units::list<boost::units::dim<boost::units::mass_base_dimension, boost::units::static_rational<1> >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-1> >, boost::units::dimensionless_type> >, boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit, boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit, boost::units::scale<10, boost::units::static_rational<3> > >, boost::units::list<boost::units::si::second_base_unit, boost::units::list<boost::units::si::ampere_base_unit, boost::units::list<boost::units::si::kelvin_base_unit, boost::units::list<boost::units::si::mole_base_unit, boost::units::list<boost::units::si::candela_base_unit, boost::units::list<boost::units::angle::radian_base_unit, boost::units::list<boost::units::angle::steradian_base_unit, boost::units::dimensionless_type> > > > > > > > > >, void> >::type {aka boost::units::quantity<boost::units::unit<boost::units::list<boost::units::dim<boost::units::mass_base_dimension, boost::units::static_rational<1> >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-1> >, boost::units::dimensionless_type> >, boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit, boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit, boost::units::scale<10, boost::units::static_rational<3> > >, boost::units::list<boost::units::si::second_base_unit, boost::units::list<boost::units::si::ampere_base_unit, boost::units::list<boost::units::si::kelvin_base_unit, boost::units::list<boost::units::si::mole_base_unit, boost::units::list<boost::units::si::candela_base_unit, boost::units::list<boost::units::angle::radian_base_unit, boost::units::list<boost::units::angle::steradian_base_unit, boost::units::dimensionless_type> > > > > > > > > >, void>, double>}’ to non-scalar type ‘Units::MassFlowRate {aka boost::units::quantity<boost::units::list<boost::units::dim<boost::units::mass_base_dimension, boost::units::static_rational<1> >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-1> >, boost::units::dimensionless_type> >, double>}’ requested
   Units::MassFlowRate other_mass_flow = 1.0*(Units::SI::kilogram / Units::SI::second);

main.cc:39:38: error: conversion from ‘boost::units::multiply_typeof_helper<boost::units::quantity<boost::units::list<boost::units::dim<boost::units::mass_base_dimension, boost::units::static_rational<1> >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-1> >, boost::units::dimensionless_type> >, double>, boost::units::quantity<boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<1> >, boost::units::dimensionless_type>, boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit, boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit, boost::units::scale<10, boost::units::static_rational<3> > >, boost::units::list<boost::units::si::second_base_unit, boost::units::list<boost::units::si::ampere_base_unit, boost::units::list<boost::units::si::kelvin_base_unit, boost::units::list<boost::units::si::mole_base_unit, boost::units::list<boost::units::si::candela_base_unit, boost::units::list<boost::units::angle::radian_base_unit, boost::units::list<boost::units::angle::steradian_base_unit, boost::units::dimensionless_type> > > > > > > > > > >, double> >::type {aka boost::units::quantity<boost::units::quantity<boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<1> >, boost::units::dimensionless_type>, boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit, boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit, boost::units::scale<10, boost::units::static_rational<3> > >, boost::units::list<boost::units::si::second_base_unit, boost::units::list<boost::units::si::ampere_base_unit, boost::units::list<boost::units::si::kelvin_base_unit, boost::units::list<boost::units::si::mole_base_unit, boost::units::list<boost::units::si::candela_base_unit, boost::units::list<boost::units::angle::radian_base_unit, boost::units::list<boost::units::angle::steradian_base_unit, boost::units::dimensionless_type> > > > > > > > > > >, boost::units::list<boost::units::dim<boost::units::mass_base_dimension, boost::units::static_rational<1> >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-1> >, boost::units::dimensionless_type> > >, double>}’ to non-scalar type ‘Units::Mass {aka boost::units::quantity<boost::units::unit<boost::units::list<boost::units::dim<boost::units::mass_base_dimension, boost::units::static_rational<1> >, boost::units::dimensionless_type>, boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit, boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit, boost::units::scale<10, boost::units::static_rational<3> > >, boost::units::list<boost::units::si::second_base_unit, boost::units::list<boost::units::si::ampere_base_unit, boost::units::list<boost::units::si::kelvin_base_unit, boost::units::list<boost::units::si::mole_base_unit, boost::units::list<boost::units::si::candela_base_unit, boost::units::list<boost::units::angle::radian_base_unit, boost::units::list<boost::units::angle::steradian_base_unit, boost::units::dimensionless_type> > > > > > > > > > >, double>}’ requested
   Units::Mass total_flow = mass_flow * (1.0*Units::SI::second);

最佳答案

您会混淆单位,尺寸和数量。

  • 这是您的尺寸,
    typedef Units::derived_dimension<Units::mass_base_dimension, 1,
                                     Units::time_base_dimension, -1>::type MassFlowDimension;
    

    您无法根据尺寸创建数量:
    typedef Quantity<MassFlowDimension> MassFlowRate;
    

    而是先创建一个单元,然后再创建一个尺寸:
  • 您的常数应该是单位常数,而不是数量:
    typedef Quantity<MassFlowDimension> MassFlowRate;
    BOOST_UNITS_STATIC_CONSTANT(kilogram_per_seconds, MassFlowRate);
    

  • 固定

    Live On Coliru
    #include <boost/units/io.hpp>
    #include <boost/units/systems/si.hpp>
    #include <boost/units/systems/si/io.hpp>
    
    namespace Units {
        using namespace boost::units;
        namespace SI = boost::units::si;
    
        template <class U> using Quantity = quantity<U>;
    
        typedef quantity<si::mass> Mass;
        typedef quantity<si::time> Time;
    
        typedef derived_dimension<mass_base_dimension, 1, time_base_dimension, -1>::type MassFlowDimension;
        typedef unit<MassFlowDimension, si::system> MassFlow;
        typedef Quantity<MassFlow> MassFlowRate;
        BOOST_UNITS_STATIC_CONSTANT(kilogram_per_seconds, MassFlow);
    }
    
    #include <iostream>
    int main() {
        Units::MassFlowRate const mass_flow       = 7.0*Units::kilogram_per_seconds;
        Units::MassFlowRate const other_mass_flow = 1.0*(Units::SI::kilogram / Units::SI::second);
        Units::Mass         const total_flow      = mass_flow * (1.0*Units::SI::second);
    
        std::cout << "mass_flow:       " << mass_flow       << "\n";
        std::cout << "other_mass_flow: " << other_mass_flow << "\n";
        std::cout << "total_flow:      " << total_flow      << "\n";
    }
    

    版画
    mass_flow:       7 kg s^-1
    other_mass_flow: 1 kg s^-1
    total_flow:      7 kg
    

    关于c++ - 使用派生单位进行计算,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/49131986/

    10-11 22:53
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