Minecraft Turtle: BuildWall

-----------Written by Barnet-----------

function MoveUp()
  while turtle.up() == false do
    if turtle.detectUp() == true then
      turtle.digUp()
    else
      turtle.attackUp()
    end
  end
end

function MoveDown()
  while turtle.down() == false do
    if turtle.detectDown() == true then
      turtle.digDown()
    else
      turtle.attackDown()
    end
  end
end

function CheckSlot()
  Slot = turtle.getItemDetail()
  if Slot.name == "" then
    return true
  else
    return false
  end
end

function CheckMaterial(Material)
  Item = turtle.getItemDetail()
  if pcall(CheckSlot) == true then
    if Item.name == Material then
      return true
    else
      return false
    end
  else
    return false
  end
end

function Refill(Material)
  if CheckMaterial(Material) == false then
    c = 1
    while c<17 do
      turtle.select(c)
      c=c+1
      if CheckMaterial(Material) == true then
        c=17
      elseif c == 17 then
        turtle.select(1)
        print("Missing material!")
        error()
      end
    end
  end
end

function MoveForward()
  while turtle.forward() == false do
    if turtle.detect() == true then
      turtle.dig()
    else
      turtle.attack()
    end
  end
end

function BuildUp(y,Material)
  x = 0
  while x<y do
    Refill(Material)
    MoveUp()
    turtle.placeDown()
    x=x+1
  end
  MoveForward()
  MoveDown()
  x = 1
  while x<y do
    Refill(Material)
    MoveDown()
    turtle.placeUp()
    x=x+1
  end
  Refill(Material)
  MoveForward()
  turtle.turnLeft()
  turtle.turnLeft()
  turtle.place()
  turtle.turnLeft()
  turtle.turnLeft()
end

function Build(y,z,Material)
  v = 1
  while v<=z/2 do
    BuildUp(y,Material)
    v=v+1
  end
end

print()
print("Build a Wall")
print("---------------------------------------")
write("Height: ")
y = tonumber(read())
write("Length: ")
z = tonumber(read())
write("Material: ")
Material = read()
print("Building wall....")
Build(y,z,Material)
print("Done!")