class Solve::Solver

def demands(*args)
  if args.empty?
    return demand_collection
  end
  if args.length > 2
    raise ArgumentError, "Unexpected number of arguments. You gave: #{args.length}. Expected: 2 or less."
  end
  name, constraint = args
  constraint ||= ">= 0.0.0"
  if name.nil?
    raise ArgumentError, "A name must be specified. You gave: #{args}."
  end
  demand = Demand.new(self, name, constraint)
  add_demand(demand)
end