Question

我有一个元组列表：

X = [{"alpha","beta"},{"gamma","theta"}].

我想使用io_lib:format("~s", [X])以下列格式打印X作为扁平字符串：

[{"x":"alpha", "y":"beta"}, {"x":"gamma", "y":"theta"}]

我如何实现这一目标？我开始使用Map来转换列表。但我无法将其打印为字符串...（在X上给出了未绑定的变量错误）。

Answer 1

疯狂地看起来像JSON序列化！您应该查看rfc4627.erl，因为它几乎完全符合您的要求。

Answer 2

享受巧妙的技巧：

1> X = [{"alpha","beta"},{"gamma","theta"}].
2> F = fun(X) -> [[$,|H]|T] = [[$,|["{\"x\":\"",A,"\", \"y\":\"",B,"\"}"]] || {A,B} <- X], [$[,[H|T],$]] end.
#Fun<erl_eval.6.111823515>
3> io:format("~s~n", [F(X)]).
[{"x":"alpha", "y":"beta"},{"x":"gamma", "y":"theta"}]

请注意我在F中执行的所有字符串操作都是O（1）。

Answer 3

试试这个：

tuplelist_to_string(L) ->
    tuplelist_to_string(L,[]).

tuplelist_to_string([],Acc) ->
    lists:flatten(["[",
           string:join(lists:reverse(Acc),","),
           "]"]);
tuplelist_to_string([{X,Y}|Rest],Acc) ->
    S = ["{\"x\":\"",X,"\", \"y\":\"",Y,"\"}"],
    tuplelist_to_string(Rest,[S|Acc]).

然后：

1> X = [{"alpha","beta"},{"gamma","theta"}].
[{"alpha","beta"},{"gamma","theta"}]
2> io:format("~s~n",[test:tuplelist_to_string(X)]).
[{"x":"alpha", "y":"beta"},{"x":"gamma", "y":"theta"}]
ok

Answer 4

你应该这样打印：

[{A，B}，{G，T}] = X

io_lib：format（“[{x：~s，y：~s}，{x：~s，y：~s}]”，[A，B，G，T]）

在元组列表中使用Map并在Erlang中将其打印为扁平字符串

4 个答案: