redstone.getInput(help)

I'm getting the error message

dig:34: Expected string

function graveldetect()
if turtle.forward() == false then
  repeat
   turtle.dig()
  until turtle.forward() == true
else
  turtle.dig
end
turtle.forward()
turtle.digUp()
turtle.digDown()
end
function dump()
x = 1
repeat
  turtle.select(x)
  turtle.dropDown()
  x = x + 1
until x == 17
redstone.setOutput(bottom, true)
end
function dig()
y = 0
while y < 100 do
  graveldetect()
  y = y + 1
end
turtle.turnLeft()
turtle.turnLeft()
repeat
  graveldetect()
until redstone.getInput(bottom) == true
dump()
end
dig()

He runs fine right up until this bit.

repeat
graveldetect()
until redstone.getInput(bottom) == true

I'm not really sure exactly how I messed up the redstone.getInput() thing. I also tried redstone.getInput(bottom, true) == true but that just returned the same error.

The argument needs to be a string.

until rs.getInput("bottom")

Since that function only returns true or false, you don't need to compare the result to true.