/*

Copyright (C) 2014 David Spies

This file is part of Octave.

Octave 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.

Octave 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 Octave; see the file COPYING.  If not, see
<http://www.gnu.org/licenses/>.

*/
#if !defined (octave_direction_h)
#define octave_direction_h 1

// Simple generic parameterized functions for stepping "forward" or "backward"
// FORWARD and BACKWARD are elements of the "direction enum
//
enum direction
{
  FORWARD = 1, BACKWARD = -1
};

// A struct with two overloaded functions: begin(lo, hi) and
// is_ended (i, lo, hi) where i is assumed to be stepping through the range
// [lo, hi) (inclusive, exclusive).  begin() returns the initial value for i
// and is_ended (i, lo, hi) returns true if i has stepped past the end of the
// range.  To increment i in the proper direction, one can simply say i += dir
// (dir is implicitly cast to an int either 1 or -1 for FORWARD and BACKWARD
// respectively).
// When lo = 0, one can instead use the 1- and 2- argument variants of begin
// and is_ended respectively
template<direction dir>
struct dir_handler
{
  octave_idx_type
  begin (octave_idx_type size) const
  {
    return begin (0, size);
  }

  octave_idx_type
  begin (octave_idx_type lo, octave_idx_type hi) const
  {
    switch (dir) {
      case FORWARD: return lo;
      case BACKWARD: return hi - 1;
    }
  }

  bool
  is_ended (octave_idx_type i, octave_idx_type size) const
  {
    return is_ended (i, 0, size);
  }

  bool
  is_ended (octave_idx_type i, octave_idx_type lo, octave_idx_type hi) const
  {
    switch (dir) {
      case FORWARD: return i >= hi;
      case BACKWARD: return i < lo;
    }
  }
};

extern const dir_handler<FORWARD> fdirc;
extern const dir_handler<BACKWARD> bdirc;

#endif