int_range.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2026 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.

// This library 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
// Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



#ifndef LIBMESH_INT_RANGE_H
#define LIBMESH_INT_RANGE_H

#include "libmesh/libmesh_common.h" // cast_int

// C++ includes
#include <vector>

namespace libMesh
{

// Forward declarations
template <typename T> class DenseSubVector;
template <typename T> class DenseVector;
template <typename T> class NumericVector;

template <typename T>
class IntRange
{
public:
  class iterator {
  public:
    using iterator_category = std::input_iterator_tag;
    using value_type = T;
    using difference_type = T;
    using pointer = T;
    using reference = T&;

    explicit iterator (T i) : _i(i) {}

    T operator* () const { return _i; }

    const iterator & operator++ ()
    {
      ++_i;
      return *this;
    }

    iterator operator++ (int)
    {
      iterator returnval(*this);
      ++_i;
      return returnval;
    }

    template <typename T2>
    void operator+= (T2 n)
    {
      _i += cast_int<T>(n);
    }

    template <typename T2>
    iterator operator+ (T2 n) const
    {
      iterator returnval(_i);
      returnval += n;
      return returnval;
    }

    bool operator== (const iterator & j) const
    {
      return ( _i == j._i );
    }

    bool operator!= (const iterator & j) const
    {
      return !(*this == j);
    }

  private:
    T _i;
  };

  typedef typename IntRange<T>::iterator const_iterator;

  template <typename U, typename V>
  IntRange(U begin, V end) :
    _begin(cast_int<T>(begin)),
    _end(cast_int<T>(end))
  {}

  // Signature needed for use in threads_pthread.h
  IntRange(const IntRange &,
           const const_iterator & begin,
           const const_iterator & end) :
    _begin(begin),
    _end(end)
  {}

  iterator begin() const { return _begin; }

  iterator end () const { return _end; }

  std::size_t size () const
  { return *_end - *_begin; }

  // For thread splitting control
  std::size_t grainsize () const { return libMesh::default_grainsize(); }

private:
  iterator _begin, _end;
};


template <typename T, typename T2>
typename IntRange<T>::iterator operator+ (T2 n, typename IntRange<T>::iterator i)
{
  return i + n;
}


template <typename T>
auto index_range(const T & sizable)
{
  return IntRange<decltype(sizable.size())>(0, sizable.size());
}


template <typename T>
IntRange<numeric_index_type> index_range(const NumericVector<T> & vec)
{
  return {vec.first_local_index(), vec.last_local_index()};
}



template <typename T>
IntRange<T> make_range(T beg, T end)
{
  return {beg, end};
}



template <typename T>
IntRange<T> make_range(T end)
{
  return {T(0), end};
}

} // namespace libMesh

#endif // LIBMESH_INT_RANGE_H