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- // ratio_test.cpp ----------------------------------------------------------//
- // Copyright 2008 Howard Hinnant
- // Copyright 2008 Beman Dawes
- // Distributed under the Boost Software License, Version 1.0.
- // See http://www.boost.org/LICENSE_1_0.txt
- #include <iostream>
- #include <boost/ratio/ratio.hpp>
- #include "duration.hpp"
- namespace User1
- {
- // Example type-safe "physics" code interoperating with chrono::duration types
- // and taking advantage of the std::ratio infrastructure and design philosophy.
- // length - mimics chrono::duration except restricts representation to double.
- // Uses boost::ratio facilities for length units conversions.
- template <class Ratio>
- class length
- {
- public:
- typedef Ratio ratio;
- private:
- double len_;
- public:
- length() : len_(1) {}
- length(const double& len) : len_(len) {}
- // conversions
- template <class R>
- length(const length<R>& d)
- : len_(d.count() * boost::ratio_divide<Ratio, R>::type::den /
- boost::ratio_divide<Ratio, R>::type::num) {}
- // observer
- double count() const {return len_;}
- // arithmetic
- length& operator+=(const length& d) {len_ += d.count(); return *this;}
- length& operator-=(const length& d) {len_ -= d.count(); return *this;}
- length operator+() const {return *this;}
- length operator-() const {return length(-len_);}
- length& operator*=(double rhs) {len_ *= rhs; return *this;}
- length& operator/=(double rhs) {len_ /= rhs; return *this;}
- };
- // Sparse sampling of length units
- typedef length<boost::ratio<1> > meter; // set meter as "unity"
- typedef length<boost::centi> centimeter; // 1/100 meter
- typedef length<boost::kilo> kilometer; // 1000 meters
- typedef length<boost::ratio<254, 10000> > inch; // 254/10000 meters
- // length takes ratio instead of two integral types so that definitions can be made like so:
- typedef length<boost::ratio_multiply<boost::ratio<12>, inch::ratio>::type> foot; // 12 inchs
- typedef length<boost::ratio_multiply<boost::ratio<5280>, foot::ratio>::type> mile; // 5280 feet
- // Need a floating point definition of seconds
- typedef boost_ex::chrono::duration<double> seconds; // unity
- // Demo of (scientific) support for sub-nanosecond resolutions
- typedef boost_ex::chrono::duration<double, boost::pico> picosecond; // 10^-12 seconds
- typedef boost_ex::chrono::duration<double, boost::femto> femtosecond; // 10^-15 seconds
- typedef boost_ex::chrono::duration<double, boost::atto> attosecond; // 10^-18 seconds
- // A very brief proof-of-concept for SIUnits-like library
- // Hard-wired to floating point seconds and meters, but accepts other units (shown in testUser1())
- template <class R1, class R2>
- class quantity
- {
- double q_;
- public:
- typedef R1 time_dim;
- typedef R2 distance_dim;
- quantity() : q_(1) {}
- double get() const {return q_;}
- void set(double q) {q_ = q;}
- };
- template <>
- class quantity<boost::ratio<1>, boost::ratio<0> >
- {
- double q_;
- public:
- quantity() : q_(1) {}
- quantity(seconds d) : q_(d.count()) {} // note: only User1::seconds needed here
- double get() const {return q_;}
- void set(double q) {q_ = q;}
- };
- template <>
- class quantity<boost::ratio<0>, boost::ratio<1> >
- {
- double q_;
- public:
- quantity() : q_(1) {}
- quantity(meter d) : q_(d.count()) {} // note: only User1::meter needed here
- double get() const {return q_;}
- void set(double q) {q_ = q;}
- };
- template <>
- class quantity<boost::ratio<0>, boost::ratio<0> >
- {
- double q_;
- public:
- quantity() : q_(1) {}
- quantity(double d) : q_(d) {}
- double get() const {return q_;}
- void set(double q) {q_ = q;}
- };
- // Example SI-Units
- typedef quantity<boost::ratio<0>, boost::ratio<0> > Scalar;
- typedef quantity<boost::ratio<1>, boost::ratio<0> > Time; // second
- typedef quantity<boost::ratio<0>, boost::ratio<1> > Distance; // meter
- typedef quantity<boost::ratio<-1>, boost::ratio<1> > Speed; // meter/second
- typedef quantity<boost::ratio<-2>, boost::ratio<1> > Acceleration; // meter/second^2
- template <class R1, class R2, class R3, class R4>
- quantity<typename boost::ratio_subtract<R1, R3>::type, typename boost::ratio_subtract<R2, R4>::type>
- operator/(const quantity<R1, R2>& x, const quantity<R3, R4>& y)
- {
- typedef quantity<typename boost::ratio_subtract<R1, R3>::type, typename boost::ratio_subtract<R2, R4>::type> R;
- R r;
- r.set(x.get() / y.get());
- return r;
- }
- template <class R1, class R2, class R3, class R4>
- quantity<typename boost::ratio_add<R1, R3>::type, typename boost::ratio_add<R2, R4>::type>
- operator*(const quantity<R1, R2>& x, const quantity<R3, R4>& y)
- {
- typedef quantity<typename boost::ratio_add<R1, R3>::type, typename boost::ratio_add<R2, R4>::type> R;
- R r;
- r.set(x.get() * y.get());
- return r;
- }
- template <class R1, class R2>
- quantity<R1, R2>
- operator+(const quantity<R1, R2>& x, const quantity<R1, R2>& y)
- {
- typedef quantity<R1, R2> R;
- R r;
- r.set(x.get() + y.get());
- return r;
- }
- template <class R1, class R2>
- quantity<R1, R2>
- operator-(const quantity<R1, R2>& x, const quantity<R1, R2>& y)
- {
- typedef quantity<R1, R2> R;
- R r;
- r.set(x.get() - y.get());
- return r;
- }
- // Example type-safe physics function
- Distance
- compute_distance(Speed v0, Time t, Acceleration a)
- {
- return v0 * t + Scalar(.5) * a * t * t; // if a units mistake is made here it won't compile
- }
- } // User1
- // Exercise example type-safe physics function and show interoperation
- // of custom time durations (User1::seconds) and standard time durations (std::hours).
- // Though input can be arbitrary (but type-safe) units, output is always in SI-units
- // (a limitation of the simplified Units lib demoed here).
- int main()
- {
- //~ typedef boost::ratio<8, BOOST_INTMAX_C(0x7FFFFFFFD)> R1;
- //~ typedef boost::ratio<3, BOOST_INTMAX_C(0x7FFFFFFFD)> R2;
- typedef User1::quantity<boost::ratio_subtract<boost::ratio<0>, boost::ratio<1> >::type,
- boost::ratio_subtract<boost::ratio<1>, boost::ratio<0> >::type > RR;
- //~ typedef boost::ratio_subtract<R1, R2>::type RS;
- //~ std::cout << RS::num << '/' << RS::den << '\n';
- std::cout << "*************\n";
- std::cout << "* testUser1 *\n";
- std::cout << "*************\n";
- User1::Distance d(( User1::mile(110) ));
- boost_ex::chrono::hours h((2));
- User1::Time t(( h ));
- //~ boost_ex::chrono::seconds sss=boost_ex::chrono::duration_cast<boost_ex::chrono::seconds>(h);
- //~ User1::seconds sss((120));
- //~ User1::Time t(( sss ));
- //typedef User1::quantity<boost::ratio_subtract<User1::Distance::time_dim, User1::Time::time_dim >::type,
- // boost::ratio_subtract<User1::Distance::distance_dim, User1::Time::distance_dim >::type > R;
- RR r=d / t;
- //r.set(d.get() / t.get());
- User1::Speed rc= r;
- (void)rc;
- User1::Speed s = d / t;
- std::cout << "Speed = " << s.get() << " meters/sec\n";
- User1::Acceleration a = User1::Distance( User1::foot(32.2) ) / User1::Time() / User1::Time();
- std::cout << "Acceleration = " << a.get() << " meters/sec^2\n";
- User1::Distance df = compute_distance(s, User1::Time( User1::seconds(0.5) ), a);
- std::cout << "Distance = " << df.get() << " meters\n";
- std::cout << "There are " << User1::mile::ratio::den << '/' << User1::mile::ratio::num << " miles/meter";
- User1::meter mt = 1;
- User1::mile mi = mt;
- std::cout << " which is approximately " << mi.count() << '\n';
- std::cout << "There are " << User1::mile::ratio::num << '/' << User1::mile::ratio::den << " meters/mile";
- mi = 1;
- mt = mi;
- std::cout << " which is approximately " << mt.count() << '\n';
- User1::attosecond as(1);
- User1::seconds sec = as;
- std::cout << "1 attosecond is " << sec.count() << " seconds\n";
- std::cout << "sec = as; // compiles\n";
- sec = User1::seconds(1);
- as = sec;
- std::cout << "1 second is " << as.count() << " attoseconds\n";
- std::cout << "as = sec; // compiles\n";
- std::cout << "\n";
- return 0;
- }
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