build_wall.lua

local l,w,h = ...
local function slot_plus() turtle.select(turtle.getSelectedSlot()%16+1) end
local function build_line(n)
    for i=1,n do
        if not turtle.placeDown() then
            slot_plus()
            turtle.placeDown()
        end
        while not turtle.getItemCount() do slot_plus() end
        turtle.forward()
    end
end
local function build_layer(l,w)
    build_line(l-1)
    turtle.turnLeft()
    build_line(w-1)
    turtle.turnLeft()
    build_line(l-1)
    turtle.turnLeft()
    build_line(w-1)
    turtle.turnLeft()
end
local function build_wall(l,w,h)
    for i=1,h do
        turtle.up()
        build_layer(l,w)
    end
end

if not l then
    error("Must have three arguments: length, width and height.")
end
if tonumber(l) and tonumber(w) and tonumber(h) then
    build_wall(l,w,h)
end
return {build=build_wall}