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