erlang when 用法

  1 -module(when_test).
  2 -export([test/1]).                                                                                                                      
  3
  4 test(Content)->
  5         Result = change(Content),
  6         io:format("The result is ~p~n",[Result]).
  7
  8 change(Content) when is_binary(Content)->
  9         erlang:binary_to_list(Content);
 10 change(Content) when is_integer(Content)->
 11         erlang:integer_to_list(Content);
 12 change(Content) when is_list(Content)->
 13         Content.
 14