class Parser::Builders::Default

def arg_prefix_map(op_t, name_t=nil) 

def arg_prefix_map(op_t, name_t=nil)
  if name_t.nil?
    expr_l = loc(op_t)
  else
    expr_l = loc(op_t).join(loc(name_t))
  end
  Source::Map::Variable.new(loc(name_t), expr_l)
end