#
# grid:
#
# A grid represents a discretization of an interval of the x-axis.
#

printf("grid procedures:  \
create_grid, \
get_n_cells_of_grid, \
get_spacing_of_grid, \
get_interval_of_grid");


create_grid := proc(x_min, x_max, n_cells)

#
# Create a uniformly-spaced grid.
#
# The return value from create_grid(), call it g, is the new grid.
# The grid extends from x_min to x_max and is divided into n_cells
# cells.  The grid points are located at the edges of cells, and
# are numbered from j = 0, ..., n_cells.  The position of the grid
# point j is g[j].
#

  local grid, dx, j;

  grid := array(0..n_cells);
  dx := evalf((x_max - x_min)/n_cells);
  for j from 0 to n_cells do
    grid[j] := x_min + j*dx;
  od;
  grid
end:


get_n_cells_of_grid := proc(grid)

#
# Return the number of cells in the grid.
#

  op(2,op(2,eval(g)))
end:


get_spacing_of_grid := proc(grid)

#
# Return grid spacing, i.e., the length of each grid cell.
#

  grid[1] - grid[0]
end:

get_interval_of_grid := proc(grid)

#
# Return endpoints [x_min, x_max] of the grid.
#

  [grid[0], grid[get_n_cells_of_grid(grid)]]
end: