Lookup table in Berry programming language

lookup.be

def lookup(x)
  x = 1.0 * x # convert to float
  var xl = [0., 1., 2., 3., 9., 10.]
  var yl = [0., 1., 2., 3., 9., 10.] # this would typically contain other values
  var n = size(xl)

  if x <= xl[0]
    return yl[0]

  elif x >= xl[n - 1]
    return yl[n - 1]

  else
    for i : 0..(n - 2)
      var x1 = xl[i]
      var x2 = xl[i + 1]
      if x >= x1 && x <= x2
        var y1 = yl[i]
        var y2 = yl[i + 1]
        return ((x - x1) / (x2 - x1)) * (y2 - y1) + y1
      end
    end # for
  end # else 
end # def