将 boost.units 中的单位从 Angular_velocity 转换为 Degrees_per_Second

Question

我需要将一般的 angle_velocity 转换为度/秒。

为了说明这个问题，示例 boostUnits.cpp：

#include <boost/units/systems/si.hpp>
#include <boost/units/systems/angle/revolutions.hpp>
#include <boost/units/systems/angle/degrees.hpp>
#include <boost/units/conversion.hpp>
#include <boost/units/pow.hpp>
#include <iostream>
#include <iterator>
#include <algorithm>

int main()
{
  boost::units::quantity< boost::units::si::angular_velocity> m_speed(
    (30.0*boost::units::si::radians_per_second)
  );
  std::cout << "m_speed: " << m_speed << std::endl;

  uint32_t result = static_cast<uint32_t>(
    boost::units::quantity<boost::units::si::angular_velocity,uint32_t>(
      m_speed*boost::units::degree::degrees/boost::units::si::seconds
    ).value()
  );
  std::cout << " result: "<< result << std::endl;

  return(0);
}

产生以下编译器输出：

g++ boostUnits.cpp
/usr/local/include/boost/units/detail/conversion_impl.hpp: In static member function ‘static boost::units::quantity<Unit2, T2> boost::units::conversion_helper<boost::units::quantity<Unit1, T1>, boost::units::quantity<Unit2, T2> >::convert(const boost::units::quantity<Unit1, T1>&) [with Unit1 = boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<2l, 1l> >, boost::units::dimensionless_type> >, boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::angle::degree_base_unit, boost::units::static_rational<1l, 1l> >, boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::heterogeneous_system_dim<boost::units::angle::radian_base_unit, boost::units::static_rational<1l, 1l> >, boost::units::dimensionless_type> > >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<2l, 1l> >, boost::units::dimensionless_type> >, boost::units::dimensionless_type> >, void>, T1 = double, Unit2 = boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000001l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<1l, 1l> >, 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<10l, boost::units::static_rational<3l, 1l> > >, 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>, T2 = unsigned int]’:
/usr/local/include/boost/units/quantity.hpp:193:   instantiated from ‘boost::units::quantity<Unit, Y>::quantity(const boost::units::quantity<Unit2, YY>&, typename boost::disable_if<boost::mpl::and_<typename boost::units::is_implicitly_convertible<Unit2, Unit>::type, boost::units::detail::is_non_narrowing_conversion<YY, Y>, mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true> >, typename boost::units::detail::disable_if_is_same<Unit, Unit2>::type>::type*) [with Unit2 = boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<2l, 1l> >, boost::units::dimensionless_type> >, boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::angle::degree_base_unit, boost::units::static_rational<1l, 1l> >, boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::heterogeneous_system_dim<boost::units::angle::radian_base_unit, boost::units::static_rational<1l, 1l> >, boost::units::dimensionless_type> > >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<2l, 1l> >, boost::units::dimensionless_type> >, boost::units::dimensionless_type> >, void>, YY = double, Unit = boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000001l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<1l, 1l> >, 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<10l, boost::units::static_rational<3l, 1l> > >, 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>, Y = unsigned int]’
boostUnits.cpp:16:   instantiated from here
/usr/local/include/boost/units/detail/conversion_impl.hpp:345: error: no matching function for call to ‘conversion_factor(boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<2l, 1l> >, boost::units::dimensionless_type> >, boost::units::heterogeneous_system<boost::units::heterogeneous_system_impl<boost::units::list<boost::units::heterogeneous_system_dim<boost::units::angle::degree_base_unit, boost::units::static_rational<1l, 1l> >, boost::units::list<boost::units::heterogeneous_system_dim<boost::units::si::second_base_unit, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::heterogeneous_system_dim<boost::units::angle::radian_base_unit, boost::units::static_rational<1l, 1l> >, boost::units::dimensionless_type> > >, boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000002l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<2l, 1l> >, boost::units::dimensionless_type> >, boost::units::dimensionless_type> >, void>&, boost::units::unit<boost::units::list<boost::units::dim<boost::units::time_base_dimension, boost::units::static_rational<-0x000000001l, 1l> >, boost::units::list<boost::units::dim<boost::units::plane_angle_base_dimension, boost::units::static_rational<1l, 1l> >, 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<10l, boost::units::static_rational<3l, 1l> > >, 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>&)’

实现所需类型规范和后续转换的语法是什么？ 我是否需要指定 Degrees_per_Second 单位？如果需要，如何指定？

文档： http://www.boost.org/doc/ libs/1_37_0/doc/html/boost_units.html

预先感谢您的帮助。

Answer 1

Steven Wantabe 在 boost-users 邮件列表上提供了解决方案。
我在下面实现了一个工作示例。

boostUnits.cpp：

#include <boost/units/systems/si.hpp>
#include <boost/units/systems/angle/revolutions.hpp>
#include <boost/units/systems/angle/degrees.hpp>
#include <boost/units/conversion.hpp>
#include <boost/units/pow.hpp>
#include <boost/units/io.hpp>
#include <iostream>
#include <iterator>
#include <algorithm>

  typedef boost::units::divide_typeof_helper<
      boost::units::degree::plane_angle,
      boost::units::si::time
  >::type degrees_per_second;

int main()
{

  boost::units::quantity< boost::units::si::angular_velocity> m_speed(
    (30.0*boost::units::si::radians_per_second)
  );

  std::cout << "m_speed rad/sec: " << m_speed << std::endl;

  std::cout << "m_speed deg/sec: " << 
    static_cast<
      boost::units::quantity<degrees_per_second> 
    >(m_speed) << 
    std::endl;

  uint32_t result = static_cast<uint32_t>(
    static_cast<
      boost::units::quantity<degrees_per_second> 
    >(m_speed).value());

  std::cout << "int result: "<< result << std::endl;

  return(0);
}

终端输出：

g++ boostUnits.cpp
./a.out 
m_speed rad/sec: 30 s^-1 rad
m_speed deg/sec: 1718.87 deg s^-1
int result: 1718

Answer 2

你不需要那么多代码。自然代数可以帮助你实现这一目标。

#include<boost/units/systems/si/io.hpp>
#include<boost/units/systems/cgs/io.hpp>
#include <boost/units/systems/angle/degrees.hpp>

#include<boost/units/cmath.hpp>
#include<iostream>

using std::cout;
using namespace boost::units;

int main(){

    quantity<si::angular_velocity> m_speed = 30.*si::radian/si::second ;
    cout 
        << m_speed << '\n'
        << m_speed/(degree::degree/si::second) << '\n'
        << quantity<si::dimensionless>(m_speed/(degree::degree/si::second))*(degree::degree/si::second) << '\n'
        << (quantity<si::dimensionless>(m_speed/(degree::degree/si::second))*(degree::degree/si::second)).value() << '\n'
        << int((quantity<si::dimensionless>(m_speed/(degree::degree/si::second))*(degree::degree/si::second)).value())
    ;   
}

输出：

30 s^-1 rad
30 deg^-1 rad
1718.87 deg s^-1
1718.87
1718