cell_types.h

// Copyright (C) 2019-2026 Garth N. Wells
//
// This file is part of DOLFINx (https://www.fenicsproject.org)
//
// SPDX-License-Identifier:    LGPL-3.0-or-later
 
#pragma once
 
#include <array>
#include <basix/cell.h>
#include <dolfinx/graph/AdjacencyList.h>
#include <map>
#include <set>
#include <string>
#include <vector>
 
namespace dolfinx::mesh
{
enum class CellType : std::int8_t
{
  // NOTE: Simplex cells have index > 0, see mesh::is_simplex
  point = 1,
  interval = 2,
  triangle = 3,
  tetrahedron = 4,
  quadrilateral = -4,
  pyramid = -5,
  prism = -6,
  hexahedron = -8
};

std::string to_string(CellType type);

CellType to_type(const std::string& cell);

inline int cell_dim(CellType type)
{
  switch (type)
  {
  case CellType::point:
    return 0;
  case CellType::interval:
    return 1;
  case CellType::triangle:
    return 2;
  case CellType::quadrilateral:
    return 2;
  case CellType::tetrahedron:
    return 3;
  case CellType::hexahedron:
    return 3;
  case CellType::prism:
    return 3;
  case CellType::pyramid:
    return 3;
  default:
    throw std::runtime_error("Unsupported cell type");
  }
}

inline CellType cell_facet_type(CellType type, int index)
{
  switch (type)
  {
  case CellType::point:
    return CellType::point;
  case CellType::interval:
    return CellType::point;
  case CellType::triangle:
    return CellType::interval;
  case CellType::tetrahedron:
    return CellType::triangle;
  case CellType::quadrilateral:
    return CellType::interval;
  case CellType::pyramid:
    if (index == 0)
      return CellType::quadrilateral;
    else
      return CellType::triangle;
  case CellType::prism:
    if (index == 0 or index == 4)
      return CellType::triangle;
    else
      return CellType::quadrilateral;
  case CellType::hexahedron:
    return CellType::quadrilateral;
  default:
    throw std::runtime_error("Unknown cell type.");
  }
}

inline CellType cell_entity_type(CellType type, int d, int index)
{
  if (int dim = mesh::cell_dim(type); d == dim)
    return type;
  else if (d == 1)
    return CellType::interval;
  else if (d == (dim - 1))
    return mesh::cell_facet_type(type, index);
  else
    return CellType::point;
}

graph::AdjacencyList<int> get_entity_vertices(CellType type, int dim);

graph::AdjacencyList<int> get_sub_entities(CellType type, int dim0, int dim1);

int cell_num_entities(CellType type, int dim);

bool is_simplex(CellType type);

int num_cell_vertices(CellType type);
 
// [dim, entity] -> closure{sub_dim, (sub_entities)}

std::map<std::array<int, 2>, std::vector<std::set<int>>>
cell_entity_closure(CellType cell_type);

basix::cell::type cell_type_to_basix_type(CellType celltype);

CellType cell_type_from_basix_type(basix::cell::type celltype);
 
} // namespace dolfinx::mesh