Erlang--->>>lists:keyfind VS ets:lookup

lists:keyfind("hello",2,L)  这里的hello不是Key,ets里面才有Key一说。
返回第一个满足条件的
如果查找结果为空返回false
ets:lookup(etsName,Key)
返回多条记录组成的List。


 ets:new(roomdata, [duplicate_bag, public, named_table, {keypos, 1}]).
ets:insert(roomdata,{"hello",2}).
ets:insert(roomdata,{"hello",2}).
L=ets:lookup(roomdata,"hello").
%% L=[{"hello",2},{"hello",2}].
LL=lists:keyfind("hello",1,L).
%%LL={"hello",2}

ets转换为List

1)ets:match(roomdata,$1) //$1表示提取元组

2)ets:match_object(roomdata,{_,_}). // {‘_’,‘_’}这里有两个通配符_是因为roomdata中一个元组有两个元素。

两者区别：1)的结果是[ [ {"hello",2} ], [ {"hello",2} ],...],

2)的结果是[ {"hello",2} , { "hello",2 },...]。

问题一：【{1,"a"},{1,"b"},{1,"c"}，...】
请问怎样一次性提取出"a","b","c"。我想到循环使用lists:keyfind+ets:delete,这太low
 1）
ets:new(roomdata, [duplicate_bag, public, named_table, {keypos, 1}]).
ets:insert(roomdata,{"hello",2}).
ets:insert(roomdata,{"hello",2}).
ets:insert(roomdata,{"hello",2}).
[K||{_,K}<- ets:lookup(roomdata,"hello")].
%[2,2,2]
 2）
用proplists:get_all_values(key,list)

proplists:get_all_values("hello",L).

%[2,3]

问题二：【{1,"a"},{2,"a"},{3,"a"}，...】如何提取出1,2,3

[A||{A,_}<-ets:match_object(roomdata,{_,"a"})].

%[1,2,3]

http://www.cnblogs.com/me-sa/archive/2011/08/11/erlang0007.html

@doonething@163.com