Explicit.hxx

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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
 * Copyright (c) 2025, Davide Stocco and Enrico Bertolazzi.                                      *
 *                                                                                               *
 * The Sandals project is distributed under the BSD 2-Clause License.                            *
 *                                                                                               *
 * Davide Stocco                                                               Enrico Bertolazzi *
 * University of Trento                                                     University of Trento *
 * e-mail: davide.stocco@unitn.it                             e-mail: enrico.bertolazzi@unitn.it *
\* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
#pragma once
 
#ifndef SANDALS_EXPLICIT_SYSTEM_HXX
#define SANDALS_EXPLICIT_SYSTEM_HXX
 
namespace Sandals {
 
  /*\
   |   _____            _ _      _ _
   |  | ____|_  ___ __ | (_) ___(_) |_
   |  |  _| \ \/ / '_ \| | |/ __| | __|
   |  | |___ >  <| |_) | | | (__| | |_
   |  |_____/_/\_\ .__/|_|_|\___|_|\__|
   |             |_|
  \*/

  template <Integer N, Integer M>
  class Explicit : public Implicit<N, M>
  {
  public:
    using Pointer  = std::shared_ptr<Explicit<N, M>>;   
    using VectorF  = typename Implicit<N, M>::VectorF;  
    using MatrixJF = typename Implicit<N, M>::MatrixJF; 
    using Type     = typename Implicit<N, M>::Type;     
 
  protected:

    Explicit(Type t_type, std::string t_name) : Implicit<N, M>(t_type, t_name) {}
 
  public:

    Explicit() : Implicit<N, M>(Type::EXPLICIT, "(missing name)") {}

    Explicit(std::string t_name) : Implicit<N, M>(Type::EXPLICIT, t_name) {}

    VectorF F(VectorF const &x, VectorF const &x_dot, Real t) const override
    {
      return x_dot - this->f(x, t);
    }

    MatrixJF JF_x(VectorF const &x, VectorF const &/*x_dot*/, Real t) const override
    {
      return -this->Jf_x(x, t);
    }

    MatrixJF JF_x_dot(VectorF const &/*x*/, VectorF const &/*x_dot*/, Real /*t*/) const override
    {
      return MatrixJF::Identity();
    }

    virtual VectorF f(VectorF const &x, Real t) const = 0;

    virtual MatrixJF Jf_x(VectorF const &x, Real t) const = 0;

    VectorF f_reverse(VectorF const &x, Real t) const
    {
      return -this->f(x, -t);
    }

    MatrixJF Jf_x_reverse(VectorF const &x, Real t) const
    {
      return -this->Jf_x(x, -t);
    }

    VectorF F_reverse(VectorF const &x, VectorF const &x_dot, Real t) const
    {
      return -x_dot - this->f(x, -t);
    }

    MatrixJF JF_x_reverse(VectorF const &x, VectorF const &/*x_dot*/, Real t) const
    {
      return -this->Jf_x(x, -t);
    }

    MatrixJF JF_x_dot_reverse(VectorF const &/*x*/, VectorF const &/*x_dot*/, Real /*t*/) const
    {
      return -MatrixJF::Identity();
    }
 
  }; // class Explicit
 
} // namespace Sandals
 
#endif // SANDALS_EXPLICIT_SYSTEM_HXX