Ways across a tile grid: breadth-first for the fewest steps, A* for the cheapest.

{:ok, path} = Cauldron2D.Grid.Path.find(&open?/1, {0, 0}, {5, 2}, size: {6, 5})
{:ok, path} = Cauldron2D.Grid.Path.astar(&open?/1, {0, 0}, {5, 2}, size: {6, 5}, cost: &terrain/1)

The grid is a function from a cell {x, y} to whether it can be walked. A path is the cells from the first step to the goal, the start left out; the same cell as start and goal is []. :none is no way within the limit.

Options

• :size — {width, height} of the grid in cells. Required
• :wrap? — whether the edges join. Default false
• :neighbours — :four or :eight. Default :four
• :limit — how many cells may be expanded before giving up. Default 10_000
• :cost — astar/4 only: a function from a cell to the cost of stepping into it, a positive number. Default 1 everywhere