to-knuth-bendix.hpp

//
// libsemigroups - C++ library for semigroups and monoids
// Copyright (C) 2025-2026 James D. Mitchell
//
// This program 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.
//
// This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
//
 
#ifndef LIBSEMIGROUPS_TO_KNUTH_BENDIX_HPP_
#define LIBSEMIGROUPS_TO_KNUTH_BENDIX_HPP_
 
#include <type_traits>
 
#include "knuth-bendix-class.hpp"  // for KnuthBendix
#include "presentation.hpp"        // for Presentation
#include "to-presentation.hpp"     // for to<Presentation>
 
namespace libsemigroups {

  // Forward decls
 
  class FroidurePinBase;
 
  template <typename Word>
  class ToddCoxeter;
 
  enum class congruence_kind;


  template <typename Result>
  auto to(congruence_kind knd, FroidurePinBase& fpb) -> std::enable_if_t<
      std::is_same_v<KnuthBendix<typename Result::native_word_type,
                                 typename Result::rewriter_type>,
                     Result>,
      Result> {
    using Word     = typename Result::native_word_type;
    using Rewriter = typename Result::rewriter_type;
    return KnuthBendix<Word, Rewriter>(knd, to<Presentation<Word>>(fpb));
  }

  template <template <typename...> typename Thing, typename Word>
  auto to(congruence_kind knd, ToddCoxeter<Word>& tc)
      -> std::enable_if_t<std::is_same_v<Thing<Word>, KnuthBendix<Word>>,
                          KnuthBendix<Word>> {
    // TODO(1) could do a version where we convert tc to FroidurePin, then use
    // the rules of that instead?
    return KnuthBendix<Word>(knd, tc.presentation());
  }

  template <typename Result>
  auto to(congruence_kind                                 knd,
          ToddCoxeter<typename Result::native_word_type>& tc)
      -> std::enable_if_t<
          std::is_same_v<KnuthBendix<typename Result::native_word_type,
                                     typename Result::rewriter_type>,
                         Result>,
          Result> {
    using Word     = typename Result::native_word_type;
    using Rewriter = typename Result::rewriter_type;
    return KnuthBendix<Word, Rewriter>(knd, tc.presentation());
  }
 
}  // namespace libsemigroups
#endif  // LIBSEMIGROUPS_TO_KNUTH_BENDIX_HPP_