Grid

-- (x, y) is the rectangle's top-left cell; y grows downward.
grid:fill_rect(5, 3, 2, 2, 7)
print(grid:get(5, 3), grid:get(6, 4)) --> 7 7
print(grid:get(5, 2), grid:get(7, 5)) --> 0 0

local path = grid:find_path(0, 0, 7, 0, { blocked = { 1 } })
-- Both ends are included; it goes round the wall's open end.
print(#path, path[1].x, path[#path].x) --> 11 0 7
print(path[6].x, path[6].y) --> 3 5
-- Close the gap and nothing gets through.
grid:set(3, 5, 1)
print(grid:find_path(0, 0, 7, 0, { blocked = { 1 } })) --> nil

-- Positions are in cells: 0.5 is the middle of cell 0.
local agent = grid:agent({
    x = 0.5,
    y = 0.5,
    speed = 4,
    blocked = { 1 },
    repath = 0.5,
})
agent:set_target(grid, 7, 0)
print(agent.x, agent.y) --> 0.5 0.5

-- A 1 x 1 box centered in cell (1, 0) moves 3 cells right.
local x, y = grid:slide(1.5, 0.5, 3, 0, 1, 1, { solid = { 1 } })
-- It stops flush against the wall in column 3.
print(x, y) --> 2.5 0.5

local steps = grid:dijkstra({
    sources = { { x = 7, y = 0 } },
    blocked = { 1 },
})
-- Steps from the source; -1 where it cannot reach.
print(steps:get(7, 0), steps:get(4, 0), steps:get(3, 0)) --> 0 3 -1

local seen = grid:field_of_view(1, 2, { range = 4, opaque = { 1 } })
local visible = {}
for _, cell in ipairs(seen) do
    visible[cell.x .. "," .. cell.y] = true
end
-- The wall is seen; what is behind it is not.
print(visible["3,2"], visible["4,2"]) --> true nil

-- Spreads through matching cells, diagonals included.
local room = grid:flood_fill(0, 0, { match = { 0 } })
-- Every open cell: 48 cells less the 5 of the wall.
print(#room) --> 43

-- Of the 8 cells around (2, 2), 3 are wall.
print(grid:count_neighbors(2, 2, { match = { 1 } })) --> 3

local life = datumhue.grid.new(5, 5)
life:fill_rect(1, 2, 3, 1, 1)
-- Conway's rules: the row of three turns into a column.
life:automata_step({
    alive = { 1 },
    birth = { 3 },
    survival = { 2, 3 },
})
print(life:get(2, 1), life:get(2, 3), life:get(1, 2)) --> 1 1 0

local hills = datumhue.noise.perlin({ seed = 1, frequency = 0.2 })
-- Below -0.2 is water (0), up to 0.3 grass (1), above that rock (2).
grid:fill_noise(hills, {
    thresholds = { -0.2, 0.3 },
    values = { 0, 1, 2 },
})
print(grid:get(0, 0)) --> 1