Z2_field.h

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/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
 *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
 *    Author(s):       Hannah Schreiber
 *
 *    Copyright (C) 2022-24 Inria
 *
 *    Modification(s):
 *      - YYYY/MM Author: Description of the modification
 */
 
#ifndef MATRIX_FIELD_Z2_H_
#define MATRIX_FIELD_Z2_H_
 
#include <utility>
 
namespace Gudhi {
namespace persistence_fields {
 
class Z2_field_element
{
 public:
  using element_type = bool;  
  template <class T>
  using isInteger = std::enable_if_t<std::is_integral_v<T> >;
 
  Z2_field_element();
  template <typename Integer_type, class = isInteger<Integer_type> >
  Z2_field_element(Integer_type element);
  Z2_field_element(const Z2_field_element& toCopy);
  Z2_field_element(Z2_field_element&& toMove) noexcept;
 
  friend void operator+=(Z2_field_element& f1, Z2_field_element const& f2) {
    f1.element_ = (f1.element_ != f2.element_);
  }
  friend Z2_field_element operator+(Z2_field_element f1, Z2_field_element const& f2) {
    f1 += f2;
    return f1;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend void operator+=(Z2_field_element& f, const Integer_type& v) { f.element_ = (f.element_ != _get_value(v)); }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend Z2_field_element operator+(Z2_field_element f, const Integer_type& v) {
    f += v;
    return f;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend Integer_type operator+(const Integer_type& v, const Z2_field_element& f) {
    return f.element_ != _get_value(v);
  }
 
  friend void operator-=(Z2_field_element& f1, Z2_field_element const& f2) {
    f1.element_ = (f1.element_ != f2.element_);
  }
  friend Z2_field_element operator-(Z2_field_element f1, Z2_field_element const& f2) {
    f1 -= f2;
    return f1;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend void operator-=(Z2_field_element& f, const Integer_type& v) { f.element_ = (f.element_ != _get_value(v)); }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend Z2_field_element operator-(Z2_field_element f, const Integer_type& v) {
    f -= v;
    return f;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend Integer_type operator-(const Integer_type v, Z2_field_element const& f) {
    return f.element_ != _get_value(v);
  }
 
  friend void operator*=(Z2_field_element& f1, Z2_field_element const& f2) {
    f1.element_ = (f1.element_ && f2.element_);
  }
  friend Z2_field_element operator*(Z2_field_element f1, Z2_field_element const& f2) {
    f1 *= f2;
    return f1;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend void operator*=(Z2_field_element& f, const Integer_type& v) { f.element_ = (f.element_ && _get_value(v)); }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend Z2_field_element operator*(Z2_field_element f, const Integer_type& v) {
    f *= v;
    return f;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend Integer_type operator*(const Integer_type& v, Z2_field_element const& f) {
    return f.element_ && _get_value(v);
  }
 
  friend bool operator==(const Z2_field_element& f1, const Z2_field_element& f2) { return f1.element_ == f2.element_; }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend bool operator==(const Integer_type& v, const Z2_field_element& f) {
    return _get_value(v) == f.element_;
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend bool operator==(const Z2_field_element& f, const Integer_type& v) {
    return _get_value(v) == f.element_;
  }
  friend bool operator!=(const Z2_field_element& f1, const Z2_field_element& f2) { return !(f1 == f2); }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend bool operator!=(const Integer_type v, const Z2_field_element& f) {
    return !(v == f);
  }
  template <typename Integer_type, class = isInteger<Integer_type> >
  friend bool operator!=(const Z2_field_element& f, const Integer_type v) {
    return !(v == f);
  }
 
  Z2_field_element& operator=(Z2_field_element other);
  Z2_field_element& operator=(const unsigned int value);
  friend void swap(Z2_field_element& f1, Z2_field_element& f2) { std::swap(f1.element_, f2.element_); }
 
  operator unsigned int() const;
 
  Z2_field_element get_inverse() const;
  std::pair<Z2_field_element, unsigned int> get_partial_inverse(unsigned int productOfCharacteristics) const;
 
  static Z2_field_element get_additive_identity();
  static Z2_field_element get_multiplicative_identity();
  static Z2_field_element get_partial_multiplicative_identity([[maybe_unused]] unsigned int productOfCharacteristics);
  static constexpr unsigned int get_characteristic();
 
  element_type get_value() const;
 
  // static constexpr bool handles_only_z2() { return true; }
 
 private:
  element_type element_;
 
  template <typename Integer_type, class = isInteger<Integer_type> >
  static constexpr element_type _get_value(Integer_type e) {
    if constexpr (std::is_same_v<Integer_type, bool>) {
      return e;
    } else {
      return e < 2 && e >= 0 ? e : e % 2;  // returns bool, so %2 won't be negative and is optimized to &
    }
  }
};
 
inline Z2_field_element::Z2_field_element() : element_(false) {}
 
template <typename Integer_type, class>
inline Z2_field_element::Z2_field_element(Integer_type element) : element_(_get_value(element)) {}
 
inline Z2_field_element::Z2_field_element(const Z2_field_element& toCopy) : element_(toCopy.element_) {}
 
inline Z2_field_element::Z2_field_element(Z2_field_element&& toMove) noexcept
    : element_(std::exchange(toMove.element_, 0)) {}
 
inline Z2_field_element& Z2_field_element::operator=(Z2_field_element other) {
  std::swap(element_, other.element_);
  return *this;
}
 
inline Z2_field_element& Z2_field_element::operator=(unsigned int const value) {
  element_ = _get_value(value);
  return *this;
}
 
inline Z2_field_element::operator unsigned int() const { return element_; }
 
inline Z2_field_element Z2_field_element::get_inverse() const {
  return element_ ? Z2_field_element(1) : Z2_field_element();
}
 
inline std::pair<Z2_field_element, unsigned int> Z2_field_element::get_partial_inverse(
    unsigned int productOfCharacteristics) const {
  return {get_inverse(), productOfCharacteristics};
}
 
inline Z2_field_element Z2_field_element::get_additive_identity() { return Z2_field_element(); }
 
inline Z2_field_element Z2_field_element::get_multiplicative_identity() { return Z2_field_element(1); }
 
inline Z2_field_element Z2_field_element::get_partial_multiplicative_identity(
    [[maybe_unused]] unsigned int productOfCharacteristics) {
  return Z2_field_element(1);
}
 
inline constexpr unsigned int Z2_field_element::get_characteristic() { return 2; }
 
inline Z2_field_element::element_type Z2_field_element::get_value() const { return element_; }
 
}  // namespace persistence_fields
}  // namespace Gudhi
 
#endif  // MATRIX_FIELD_Z2_H_