ClearCube v0.7.5

args = {...}
width = args[1];
length = args[2];
height = args[3];

if width==nil then
    error("Width not specified");
end
if length==nil then
    error("Length not specified");
end
if height==nil then
    error("Height not specified");
end

turtle.turnRight();
for i=0, width/2-1, 1 do
    --Assuming that we were put in the centre of one side of the bottom of the cube
    -- move to the side of the cube to start.
    turtle.dig();
        while not turtle.forward() do
            turtle.dig()
        end
end
turtle.turnLeft();


function mineRow(num)
    for i=0, num, 1 do
    print("depth = " .. i);
    --Dig infront of you.
        while turtle.detect() do
            turtle.dig()
        end
    --dig infront of you if you can't move forward.
        while not turtle.forward() do
            turtle.dig()
        end
    end
end

function digPlane(x, y)
    for i=0, y, 1 do
        print("width = " .. i);
        --Mine 1 row
        mineRow(x/2);
        turtle.turnLeft();
        --Else turn around and get ready for the next one.
        mineRow(0);
        turtle.turnLeft();
        --Mine 1 row
        mineRow(x/2);
        turtle.turnRight();
        --Exit if we've finished this area.
        i = i + 1
        print("width = " .. i);
        if tonumber(i+1) >= tonumber(y) then
            break
        end
        --Mine column a little
        mineRow(0);
        turtle.turnRight();
    end
    --Turn around and get ready for the next plane.
    turtle.turnRight();
    mineRow(1);
end

function digCube(x, y, z)
    print(x)
    print(y)
    print(z)
    for i=0, z, 1 do
        print("height = " .. i);
        digPlane(x, y);
        --Dig above you
            while turtle.detectUp() do
                turtle.digUp()
            end
        --Move up
            while not turtle.up() do
                turtle.digUp()
            end
    end
end

digCube(length, width, height);