BigTreeChop

--Program to chop trees wider than 1 block. Used for tall, slender trees.
--Author: Andrew Lalis

--Tries moving forward until successful.
function safeForward()
    local success
    repeat
        success = turtle.forward()
    until (success)
end

--Chops a vertical pillar of wood.
function chopPillar()
    local success,data = turtle.inspectUp()
    local woodName = data.name
    local displacement = 0
    repeat
        turtle.digUp()
        turtle.up()
        displacement = displacement + 1
        success,data = turtle.inspectUp()
    until (data == nil or data.name ~= woodName)
    for i=1,displacement do
        turtle.down()
    end
end

--Chops one row of the tree.
function chopRow(treeSize)
    for i=1,treeSize do
        if (turtle.detect()) then
            turtle.dig()
            safeForward()
            if (turtle.detectUp()) then
                chopPillar()
            end
        else
            safeForward()
        end
    end
end

--Gets the tree size from the user.
function getTreeSize(args)
    if (args[1] ~= nil) then
        return tonumber(args[1])
    else
        print("Please enter the diameter of the tree.")
        return tonumber(read())
    end
end

local args = {...}
local treeSize = getTreeSize(args)
for i=1,treeSize do
    safeForward()
    chopRow(treeSize)
    safeForward()
    if (i % 2 == 1) then
        turtle.turnRight()
        safeForward()
        turtle.turnRight()
    else
        turtle.turnLeft()
        safeForward()
        turtle.turnLeft()
    end
end