Z2_field_operators.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) 2024 Inria
 *
 *    Modification(s):
 *      - YYYY/MM Author: Description of the modification
 */
 
#ifndef MATRIX_FIELD_Z2_OPERATORS_H_
#define MATRIX_FIELD_Z2_OPERATORS_H_
 
#include <utility>
 
namespace Gudhi {
namespace persistence_fields {
 
class Z2_field_operators
{
 public:
  using Element = bool;                
  using Characteristic = unsigned int; 
  template <class T>
  using isUnsignedInteger = std::enable_if_t<std::is_unsigned_v<T> >;
  template <class T>
  using isInteger = std::enable_if_t<std::is_integral_v<T> >;
 
  Z2_field_operators(){};
 
  static constexpr Characteristic get_characteristic() { return 2; }
 
  template <typename Integer_type, class = isInteger<Integer_type> >
  static Element 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 &
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static Element add(Unsigned_integer_type e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return e1 != e2;
    } else {
      return get_value(e1) != get_value(e2);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void add_inplace(Unsigned_integer_type& e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      e1 = e1 != e2;
    } else {
      e1 = get_value(e1) != get_value(e2);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static Element subtract(Unsigned_integer_type e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return e1 != e2;
    } else {
      return get_value(e1) != get_value(e2);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void subtract_inplace_front(Unsigned_integer_type& e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      e1 = e1 != e2;
    } else {
      e1 = get_value(e1) != get_value(e2);
    }
  }
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void subtract_inplace_back(Unsigned_integer_type e1, Unsigned_integer_type& e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      e2 = e1 != e2;
    } else {
      e2 = get_value(e1) != get_value(e2);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static Element multiply(Unsigned_integer_type e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return e1 && e2;
    } else {
      return get_value(e1) ? get_value(e2) : false;
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void multiply_inplace(Unsigned_integer_type& e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      e1 = e1 && e2;
    } else {
      e1 = get_value(e1) ? get_value(e2) : false;
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static Element multiply_and_add(Unsigned_integer_type e, Unsigned_integer_type m, Unsigned_integer_type a) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return (e && m) != a;
    } else {
      return multiply(e, m) != get_value(a);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void multiply_and_add_inplace_front(Unsigned_integer_type& e, 
                                             Unsigned_integer_type m,
                                             Unsigned_integer_type a) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      e = (e && m) != a;
    } else {
      e = multiply(e, m) != get_value(a);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void multiply_and_add_inplace_back(Unsigned_integer_type e, 
                                            Unsigned_integer_type m,
                                            Unsigned_integer_type& a) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      a = (e && m) != a;
    } else {
      a = multiply(e, m) != get_value(a);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static Element add_and_multiply(Unsigned_integer_type e, Unsigned_integer_type a, Unsigned_integer_type m) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return (e != a) && m;
    } else {
      return add(e, a) ? get_value(m) : false;
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void add_and_multiply_inplace_front(Unsigned_integer_type& e, Unsigned_integer_type a, Unsigned_integer_type m) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      e = (e != a) && m;
    } else {
      e = add(e, a) ? get_value(m) : false;
    }
  }
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static void add_and_multiply_inplace_back(Unsigned_integer_type& e, Unsigned_integer_type a, Unsigned_integer_type m) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      m = (e != a) && m;
    } else {
      m = add(e, a) ? get_value(m) : false;
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static bool are_equal(Unsigned_integer_type e1, Unsigned_integer_type e2) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return e1 == e2;
    } else {
      return get_value(e1) == get_value(e2);
    }
  }
 
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static Element get_inverse(Unsigned_integer_type e) {
    if constexpr (std::is_same_v<Unsigned_integer_type, bool>) {
      return e;
    } else {
      return get_value(e);
    }
  }
  template <typename Unsigned_integer_type, class = isUnsignedInteger<Unsigned_integer_type> >
  static std::pair<Element, Characteristic> get_partial_inverse(
      Unsigned_integer_type e, Characteristic productOfCharacteristics) {
    return {get_inverse(e), productOfCharacteristics};
  }
 
  static constexpr Element get_additive_identity() { return false; }
  static constexpr Element get_multiplicative_identity() { return true; }
  static constexpr Element get_partial_multiplicative_identity(
      [[maybe_unused]] Characteristic productOfCharacteristics) {
    return true;
  }
 
  // static constexpr bool handles_only_z2() { return true; }
};
 
}  // namespace persistence_fields
}  // namespace Gudhi
 
#endif  // MATRIX_FIELD_Z2_OPERATORS_H_