Question

我刚开始在Erlang学习，很难理解。我想将列表拆分为字符串，对其运行string:titlecase，然后将其加入字符串。

namecase(Text) ->
    TextArray = string:split(Text, " ", all),
    lists:join(" ", lists:foreach(fun(Element) -> string:titlecase(Element) end, TextArray)).

，但失败，并显示错误消息escript: exception error: no function clause matching lists:join(" ",ok) (lists.erl, line 1449)，因为它返回了ok，为什么返回正常？

Answer 1

lists:foreach不返回传递给它的函数返回的值。它应与仅引起副作用（例如打印）的功能一起使用。您正在寻找lists:map。

1> Text = "foo bar baz".
"foo bar baz"
2> TextArray = string:split(Text, " ", all).
["foo","bar","baz"]
3> lists:join(" ", lists:map(fun(Element) -> string:titlecase(Element) end, TextArray)).
["Foo"," ","Bar"," ","Baz"]

而且，匿名函数可以使用fun module:name/arity语法缩短：

4> lists:join(" ", lists:map(fun string:titlecase/1, TextArray)).
["Foo"," ","Bar"," ","Baz"]

list：foreach在Erlang中返回确定

1 个答案: