class Neighbor::SparseVector

def from_text(string)
  elements, dimensions = string.split("/", 2)
  indices = []
  values = []
  elements[1..-2].split(",").each do |e|
    index, value = e.split(":", 2)
    indices << index.to_i - 1
    values << value.to_f
  end
  from_parts(dimensions.to_i, indices, values)
end