From 2c2b69e1df183f118c45d74c18c7e84934aaff1f Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Mon, 11 Oct 2010 02:38:46 -0400
Subject: Support systems of ODEs.

---
 src/vZ/EquationSystem.hpp | 154 ++++++++++++++++++++++++++++++++++++++++++++++
 src/vZ/Integrator.hpp     |   4 +-
 2 files changed, 156 insertions(+), 2 deletions(-)
 create mode 100644 src/vZ/EquationSystem.hpp

(limited to 'src/vZ')

diff --git a/src/vZ/EquationSystem.hpp b/src/vZ/EquationSystem.hpp
new file mode 100644
index 0000000..0963baf
--- /dev/null
+++ b/src/vZ/EquationSystem.hpp
@@ -0,0 +1,154 @@
+/*************************************************************************
+ * 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_EQUATIONSYSTEM_HPP
+#define VZ_EQUATIONSYSTEM_HPP
+
+#include <cstddef>
+
+namespace vZ
+{
+  // A class to easily represent a system of ODEs
+  template <std::size_t N, typename T = double>
+  class EquationSystem
+  {
+  public:
+    typedef typename Traits<T>::Scalar Scalar;
+
+    // EquationSystem();
+    // ~EquationSystem();
+
+    T&       operator[](std::size_t i)       { return m_values[0]; }
+    const T& operator[](std::size_t i) const { return m_values[0]; }
+
+    EquationSystem& operator+=(const EquationSystem& rhs);
+    EquationSystem& operator-=(const EquationSystem& rhs);
+    EquationSystem& operator*=(Scalar rhs);
+    EquationSystem& operator/=(Scalar rhs);
+
+  private:
+    T m_values[N];
+  };
+
+  // Traits specialization
+  template <std::size_t N, typename T>
+  class Traits<EquationSystem<N, T> >
+  {
+  public:
+    typedef typename Traits<T>::Scalar Scalar;
+
+  private:
+    Traits();
+  };
+
+  // Binary operators
+
+  template <std::size_t N, typename T>
+  inline EquationSystem<N, T>
+  operator+(const EquationSystem<N, T>& lhs, const EquationSystem<N, T>& rhs)
+  {
+    EquationSystem<N, T> res = lhs;
+    res += rhs;
+    return res;
+  }
+
+  template <std::size_t N, typename T>
+  inline EquationSystem<N, T>
+  operator-(const EquationSystem<N, T>& lhs, const EquationSystem<N, T>& rhs)
+  {
+    EquationSystem<N, T> res = lhs;
+    res -= rhs;
+    return res;
+  }
+
+  template <std::size_t N, typename T>
+  inline EquationSystem<N, T>
+  operator*(typename EquationSystem<N, T>::Scalar lhs,
+            const EquationSystem<N, T>& rhs)
+  {
+    EquationSystem<N, T> res = rhs;
+    res *= lhs;
+    return res;
+  }
+
+  template <std::size_t N, typename T>
+  inline EquationSystem<N, T>
+  operator*(const EquationSystem<N, T>& lhs,
+            typename EquationSystem<N, T>::Scalar rhs)
+  {
+    EquationSystem<N, T> res = lhs;
+    res *= rhs;
+    return res;
+  }
+
+  template <std::size_t N, typename T>
+  inline EquationSystem<N, T>
+  operator/(const EquationSystem<N, T>& lhs,
+            typename EquationSystem<N, T>::Scalar rhs)
+  {
+    EquationSystem<N, T> res = lhs;
+    res /= rhs;
+    return res;
+  }
+
+  // Implementation
+
+  template <std::size_t N, typename T>
+  EquationSystem<N, T>&
+  EquationSystem<N, T>::operator+=(const EquationSystem<N, T>& rhs)
+  {
+    for (std::size_t i = 0; i < N; ++i) {
+      m_values[i] += rhs.m_values[i];
+    }
+    return *this;
+  }
+
+  template <std::size_t N, typename T>
+  EquationSystem<N, T>&
+  EquationSystem<N, T>::operator-=(const EquationSystem<N, T>& rhs)
+  {
+    for (std::size_t i = 0; i < N; ++i) {
+      m_values[i] -= rhs.m_values[i];
+    }
+    return *this;
+  }
+
+  template <std::size_t N, typename T>
+  EquationSystem<N, T>&
+  EquationSystem<N, T>::operator*=(typename EquationSystem<N, T>::Scalar rhs)
+  {
+    for (std::size_t i = 0; i < N; ++i) {
+      m_values[i] *= rhs;
+    }
+    return *this;
+  }
+
+  template <std::size_t N, typename T>
+  EquationSystem<N, T>&
+  EquationSystem<N, T>::operator/=(typename EquationSystem<N, T>::Scalar rhs)
+  {
+    for (std::size_t i = 0; i < N; ++i) {
+      m_values[i] /= rhs;
+    }
+    return *this;
+  }
+}
+
+#endif // VZ_EQUATIONSYSTEM_HPP
diff --git a/src/vZ/Integrator.hpp b/src/vZ/Integrator.hpp
index c6d6fbe..cb9649a 100644
--- a/src/vZ/Integrator.hpp
+++ b/src/vZ/Integrator.hpp
@@ -39,9 +39,9 @@ namespace vZ
     typedef typename Traits<Y>::Scalar Scalar;
     typedef std::tr1::function<Y (Scalar, Y)> Function;
 
-    // By default, y and t start at zero, h starts UNDEFINED
+    // By default, y, t, and h start UNDEFINED
     GenericIntegrator(Function f)
-      : m_f(f), m_y(0), m_x(0), m_iterations(0) { }
+      : m_f(f),m_iterations(0) { }
     virtual ~GenericIntegrator() { }
 
     GenericIntegrator& y(Y y)      { m_y = y; return *this; }
-- 
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