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/*************************************************************************
* Copyright (C) 2009-2010 Tavian Barnes <tavianator@gmail.com> *
* *
* This file is part of The vZ Library. *
* *
* The vZ Library is free software; you can redistribute it and/or *
* modify it under the terms of the GNU Lesser General Public License as *
* published by the Free Software Foundation; either version 3 of the *
* License, or (at your option) any later version. *
* *
* The vZ Library is distributed in the hope that it will be useful, but *
* WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
#ifndef VZ_INTEGRATOR_HPP
#define VZ_INTEGRATOR_HPP
#include <tr1/functional>
#include <algorithm>
namespace vZ
{
// Base Integrator class
//
// All integration methods derrive from this class
// If the initial value problem is specified as
// y' = f(t, y); y(t0) = y0
// then an Integrator could be constructed as Integrator(f, dt).y(y0).t(t0)
template <typename T>
class GenericIntegrator
{
public:
typedef std::tr1::function<T (T, T)> Function;
// By default, y and t start at zero
GenericIntegrator(Function f, T dt)
: m_f(f), m_y(0), m_t(0), m_dt(dt) { }
virtual ~GenericIntegrator() { }
GenericIntegrator& y(T y) { m_y = y; return *this; }
GenericIntegrator& t(T t) { m_t = t; return *this; }
GenericIntegrator& dt(T dt) { m_dt = dt; return *this; }
T y() const { return m_y; }
T t() const { return m_t; }
T dt() const { return m_dt; }
// Integrate until time t
void integrate(T t_final);
protected:
virtual void step(T& t, T& dt) = 0;
Function m_f;
private:
T m_y;
T m_t, m_dt;
};
// Type alias
typedef GenericIntegrator<double> Integrator;
// Implementations
template <typename T>
void
GenericIntegrator<T>::integrate(T t_final)
{
while (m_t < t_final) {
m_dt = std::min(m_dt, t_final - m_t);
step(m_t, m_dt);
}
}
}
#endif // VZ_INTEGRATOR_HPP
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