real_polyhedral_homotopy_continuation/reference/include/function_tree/symbols/variable.hpp

// This file is part of Bertini 2.
//
// include/function_tree/symbols/variable.hpp is free software: you can
// redistribute it and/or modify it under the terms of the GNU General Public
// License as published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// include/function_tree/symbols/variable.hpp 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 General
// Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with include/function_tree/symbols/variable.hpp.  If not, see
// <http://www.gnu.org/licenses/>.
//
//  Copyright(C) 2015 - 2023 by Bertini2 Development Team
//
//  See <http://www.gnu.org/licenses/> for a copy of the license,
//  as well as COPYING.  Bertini2 is provided with permitted
//  additional terms in the b2/licenses/ directory.

// individual authors of this file include:
//  James Collins
//  West Texas A&M University
//  Spring, Summer 2015
//
// silviana amethyst, university of wisconsin-eau claire
//
//  Created by Collins, James B. on 4/30/15.
//
//
// include/function_tree/symbols/variable.hpp:  Declares the class Variable.

/**
\file include/function_tree/symbols/variable.hpp

\brief Provides the Variable Node class.

*/
#ifndef BERTINI_FUNCTION_TREE_VARIABLE_HPP
#define BERTINI_FUNCTION_TREE_VARIABLE_HPP

#include "function_tree/symbols/differential.hpp"
#include "function_tree/symbols/symbol.hpp"

namespace bertini {
namespace node {
/**
\brief Represents variable leaves in the function tree.

This class represents variable leaves in the function tree.  FreshEval returns
the current value of the variable.

When differentiated, produces a differential referring to it.
*/
class Variable : public virtual NamedSymbol,
                 public virtual EnableSharedFromThisVirtual<Variable> {
 public:
  BERTINI_DEFAULT_VISITABLE()

  template <typename... Ts>
  static std::shared_ptr<Variable> Make(Ts&&... ts) {
    return std::shared_ptr<Variable>(new Variable(ts...));
  }

 private:
  Variable(std::string new_name);

 public:
  virtual ~Variable() = default;

  explicit operator std::string() { return name(); }

  // This sets the value for the variable
  template <typename T>
  void set_current_value(T const& val);

  /**
  \brief Changes the value of the variable to be not-a-number.
  */
  template <typename T>
  void SetToNan();

  /**
  \brief Changes the value of the variable to be a random complex number.
  */
  template <typename T>
  void SetToRand();

  /**
  \brief Changes the value of the variable to be a random complex number, of
  magnitude 1.
  */
  template <typename T>
  void SetToRandUnit();

  /**
   Differentiates a variable.
   */
  std::shared_ptr<Node> Differentiate(
      std::shared_ptr<Variable> const& v = nullptr) const override;

  void Reset() const override;

  /**
  Compute the degree with respect to a single variable.

  If this is the variable, then the degree is 1.  Otherwise, 0.
  */
  int Degree(std::shared_ptr<Variable> const& v = nullptr) const override;

  int Degree(VariableGroup const& vars) const override;

  std::vector<int> MultiDegree(VariableGroup const& vars) const override;

  void Homogenize(VariableGroup const& vars,
                  std::shared_ptr<Variable> const& homvar) override;

  bool IsHomogeneous(
      std::shared_ptr<Variable> const& v = nullptr) const override;

  /**
  Check for homogeneity, with respect to a variable group.
  */
  bool IsHomogeneous(VariableGroup const& vars) const override;

  /**
   Change the precision of this variable-precision tree node.

   \param prec the number of digits to change precision to.
   */
  void precision(unsigned int prec) const override;

 protected:
  // Return current value of the variable.
  dbl FreshEval_d(
      std::shared_ptr<Variable> const& diff_variable) const override;

  void FreshEval_d(
      dbl& evaluation_value,
      std::shared_ptr<Variable> const& diff_variable) const override;

  mpfr_complex FreshEval_mp(
      std::shared_ptr<Variable> const& diff_variable) const override;

  void FreshEval_mp(
      mpfr_complex& evaluation_value,
      std::shared_ptr<Variable> const& diff_variable) const override;

  Variable();

 private:
  friend class boost::serialization::access;

  template <typename Archive>
  void serialize(Archive& ar, const unsigned version) {
    ar& boost::serialization::base_object<NamedSymbol>(*this);
  }
};

}  // namespace node
}  // namespace bertini

#endif