lists模块 ################ duplicate/2 ''''''''''''''' 结构:: duplicate(N, Elem) -> List 类型 N = integer() >= 0 Elem = T List = [T] T = term() 说明:: Returns a list containing N copies of term Elem. 实例:: > lists:duplicate(5, xx). [xx,xx,xx,xx,xx] filter/2 ''''''''''''' 用法:: filter(Pred, List1) -> List2 类型 Pred = fun((Elem :: T) -> boolean()) List1 = List2 = [T] T = term() 说明:: List2是List1中的元素在执行Pred(Elem)函数时返回true的列表 filtermap/2 ''''''''''''''' 用法:: filtermap(Fun, List1) -> List2 类型: Fun = fun((Elem) -> boolean()| {true, Value}) List1 = [Elem] List2 = [Elem | Value] 说明:: 按函数Fun进行过滤 代码展示实现功能:: filtermap(Fun, List1) -> lists:foldr( fun(Elem, Acc) -> case Fun(Elem) of false -> Acc; true -> [Elem|Acc]; {true,Value} -> [Value|Acc] end end, [], List1). 实例:: > lists:filtermap( fun(X) -> case X rem 2 of 0 -> {true, X div 2}; _ -> false end end, [1,2,3,4,5]). 结果:[1,2] foreach/2 ''''''''''''' 用法:: foreach(Fun, List) -> ok 类型: Fun = fun((Elem :: T) -> term()) List = [T] T = term() 说明:: 对List中的每个元素调用Fun(Elem) 得到的结果顺序与List顺序相同 实例:: L1 = [1,2,3,4,5]. lists:foreach(fun(X) -> io:format("~p~n", [X]) end, L1). L2 = [{a1, b1}, {a2, b2}, {a3, b3}]. Fun = fun({A, _}) -> io:format("~p~n", [A]) end. lists:foreach(Fun, L2). foldl/3 ''''''''''''''' 用法:: foldl(Fun, Acc0, List) -> Acc1 类型: Fun = fun((Elem :: T, AccIn) -> AccOut) Acc0 = Acc1 = AccIn = AccOut = term() List = [T] T = term() 解释:: 遍历List, 一次次执行Fun/2函数, Fun/2函数: 第1个参数是List中的每次的值, 第2个参数初使值为Acc0, 之后每次是前一次的结果 实例:: > lists:foldl(fun(X, Sum) -> X + Sum end, 0, [1,2,3,4,5]). 15 > lists:foldl(fun(X, Prod) -> X * Prod end, 1, [1,2,3,4,5]). 120 keyfind/3 '''''''''''''' 用法:: keyfind(Key, N, TupleList) -> Tuple | false 类型: Key = term() N = integer() >= 1 1..tuple_size(Tuple) TupleList = [Tuple] Tuple = tuple() 解释:: 取出指定key对应的tuple 实例:: > lists:keyfind(a, 1, [{a,1}, {b,2}]). {a, 1} > lists:keyfind(a, 1, [{ad,1}, {b,2}, {a,a,b}]). {a, a, b} keymember/3 '''''''''''''' 用法:: keyfind(Key, N, TupleList) -> true | false 类型: Key = term() N = integer() >= 1 1..tuple_size(Tuple) TupleList = [Tuple] Tuple = tuple() 解释:: 查询tuple列表TupleList，并把它的第N个元素与Key对比是否相同 如果相同返回true，否则返回false 实例:: lists:keymember(octopus, 1, application:which_applications()). keyreplace/4 ''''''''''''''''' 用法:: keyreplace(Key, N, TupleList1, NewTuple) -> TupleList2 类型: Key = term() N = integer() >= 1; 1..tuple_size(Tuple) TupleList1 = TupleList2 = [Tuple] NewTuple = Tuple Tuple = tuple() 说明:: 如果TupleList1中的tuple的第N位的值等于Key,则把此tuple的值替换为NewTuple 实例:: %% 示例 lists:keyreplace(env, 1, AppSpec, {env, Env}). %% 实例 1> List = [{key1, value1}, {key2, value2}]. [{key1,value1},{key2,value2}] 2> lists:keyreplace(key1, 1, List, {key1, abc}). [{key1,abc},{key2,value2}] keysort/2 '''''''''''''' 用法:: keysort(N, TupleList1) -> TupleList2 类型: N = integer() >= 1 TupleList1 = TupleList2 = [Tuple] 说明:: Returns a list containing the sorted elements of list TupleList1. Sorting is performed on the Nth element of the tuples. The sort is stable. keytake/3 ''''''''''''' 用法:: keytake(Key, N, TupleList1) -> {value, Tuple, TupleList2} | false 说明:: 把TupleList1中第N列与Key对比,如果都不相同返回false, 如果相同, Tuple即为第1个与Key相同的值, TupleList2是去除了Tuple后的tuple列表 实例:: > lists:keytake(a, 1, [{ad,1}, {b,2}, {a,a,b}]). {value,{a,a,b},[{ad,1},{b,2}]} member/2 '''''''''''' 用法:: member(Elem, List) -> boolean() 类型: Elem = T List = [T] T = term() 解释:: 如果列表List中有Elem返回true，否则返回true 实例:: 1> List = [1,2,3,4,5]. [1,2,3,4,5] 2> lists:member(3, List). true partition/2 '''''''''''''''' 用法:: partition(Pred, List) -> {Satisfying, NotSatisfying} 类型: Pred = fun((Elem :: T) -> boolean()) List = Satisfying = NotSatisfying = [T] T = term() 说明:: 对列表进行区分,Pred函数执行为true的归类到Satisfying,其他的归类到NotSatisfying 实例:: > lists:partition(fun(A) -> A rem 2 == 1 end, [1,2,3,4,5,6,7]). {[1,3,5,7],[2,4,6]} > lists:partition(fun(A) -> is_atom(A) end, [a,b,1,c,d,2,3,4,e]). {[a,b,c,d,e],[1,2,3,4]} 排序相关 ''''''''''' .. function:: sort/1 :: sort(List1) -> List2 类型: List1 = List2 = [T] T = term() 说明:: Returns a list containing the sorted elements of List1. .. function:: sort/2 :: sort(Fun, List1) -> List2 类型: Fun = fun((A :: T, B :: T) -> boolean()) List1 = List2 = [T] T = term() 说明:: 基于排序函数Fun, 返回排序的列表List1 函数Fun(A, B): 如果A<=B, 则返回true; 反之返回false 实例1:: % 最简单实例 Fun = fun(A, B) -> A =< B end. List = [1, 3, 5, 2, 6, 4]. lists:sort(Fun, List). 实例2:: % 取出所有进程reductions最高的前5个进程 Fun = fun({reductions,R1}, {reductions,R2}) -> R1 > R2 end. List = [process_info(Pid, reductions) || Pid <- processes()]. lists:sublist(lists:sort(Fun, List), 5). 实例3:: % 列表中列表 Fun = fun(List1, List2) -> {reductions,R1} = lists:nth(1, List1), {reductions,R2} = lists:nth(1, List2), R1 > R2 end. List = [process_info(Pid, [reductions, registered_name]) || Pid <- processes()]. lists:sublist(lists:sort(Fun, List), 5). .. function:: split/2 :: split(N, List1) -> {List2, List3} 类型: N = integer() >= 0 0..length(List1) List1 = List2 = List3 = [T] T = term() 说明:: 拆分List1,拆分后 List2包含前N个元素 List3包含剩下的元素 .. function:: prefix/2 :: prefix(List1, List2) -> boolean() 类型 List1 = List2 = [T] T = term() 如果List1是List2的prefix返回true，否则返回false 实例:: 14 > lists:prefix([], []). true 15> lists:prefix([abc], [abc, def]). true 16> lists:prefix([abc], [abcdef]). false .. function:: zip/2 结构:: zip(List1, List2) -> List3 Types List1 = [A] List2 = [B] List3 = [{A, B}] A = B = term() 说明:: 把两个长度相同的列表List1, List2合并成一个两元素tuple的新列表的List3 实例:: $> List1 = [a, b, c]. $> List2 = [1, 2, 3]. $> lists:zip(List1, List2). [{a,1},{b,2},{c,3}] .. function:: zip3/3 结构:: zip3(List1, List2, List3) -> List4 Types List1 = [A] List2 = [B] List3 = [C] List4 = [{A, B, C}] A = B = C = term() 说明:: 参见zip/2 实例:: $> List3 = ['!', '@', '#']. $> lists:zip3(List1, List2, List3). [{a,1,'!'},{b,2,'@'},{c,3,'#'}]