json获取prolog谓词 [英] json get prolog predicate

问题描述

我正在尝试在 prolog 中创建这个谓词:

<块引用>

谓词json_get/3可以定义为:json_get(JSON_obj, Fields, Result).当Result可恢复时为真按照Fields(列表)中的字段链，从 JSON_obj 开始.一个领域由 N 表示(其中 N 主编号 o 等于 0)对应于JSON 数组的索引.

请帮助我理解遵循字段链.

谢谢

当然，所以 json 对象看起来像这样 '{"name" : "Aretha", "surname" : "Franklin"}'.如果我为此对象 prolog 调用 json_parse 谓词，请告诉我这个

json_obj([("name", "Aretha"), ("surname", "Franklin")])，我们称这个obj为O.p>

用json_get我需要这样从O中提取名字，json_get(O, ["name"], R)

在某人的帮助下，现在这是谓词:

json_get(json_obj(JSON_obj), Field, Result) :-memberchk((字段，结果)，JSON_obj).json_get(JSON_obj，字段，结果):-地图列表(json_get(JSON_obj)，字段，结果).

所以现在问题是嵌套列表.例如这个输入

json_parse('{"nome" : "Zaphod",头":[头1"，头2"]}'，Z)，json_get(Z，[头"，1]，R).

输出应该是 R = "Head2" 但谓词不提取字段并失败.

这是 json_parse 的输出

json_obj([("nome", "Zaphod"), ("heads", json_array(["Head1", "Head2"]))]).

解决方案

这个怎么样

json_get(json_obj(Obj),[F|Fs],Res) :-成员((F，R)，Obj)，json_get(R,Fs,Res).json_get(json_array(Is),[N|Fs],Res) :-nth1(N,Is,R),json_get(R,Fs,Res).json_get(Res,[],Res).

这会在您的第二个示例中生成 Head1 而不是 Head2.如果您不只是打错字，请解释​​这应该如何工作.(如果它是从零开始的，您只需将 nth1/3 更改为 nth0/3.)

I'm tryung to create this predicate in prolog:

The predicate json_get/3 can be defined as: json_get(JSON_obj, Fields, Result). which is true when Result is recoverable by following the chain of fields in Fields (a list) starting from JSON_obj. A field represented by N (with N a major number o equal to 0) corresponds to an index of a JSON array.

Please help me to understand to follow the chain of fields.

Thanks

edit1:

Of course, so json object looks like this '{"name" : "Aretha", "surname" : "Franklin"}'. if i call json_parse predicate to this object prolog show me this

json_obj([("name", "Aretha"), ("surname", "Franklin")]), we call this obj O.

with json_get i need to extract from O the name in this way, json_get(O, ["name"], R)

edit2:

with someone's help this is the predicate now:

json_get(json_obj(JSON_obj), Field, Result) :-
    memberchk((Field,Result), JSON_obj).

json_get(JSON_obj, Fields, Result) :-
    maplist(json_get(JSON_obj), Fields, Result).

so now the problem is nested list. For example with this input

json_parse('{"nome" : "Zaphod",
            "heads" : ["Head1", "Head2"]}', Z),
json_get(Z, ["heads", 1], R).

the output will should be R = "Head2" but the predicate doesn't extract the field and fail.

edit3:

this is the output of json_parse

json_obj([("nome", "Zaphod"),  ("heads", json_array(["Head1", "Head2"]))]).

解决方案

How about this

json_get(json_obj(Obj),[F|Fs],Res) :-
  member((F,R),Obj),
  json_get(R,Fs,Res).
json_get(json_array(Is),[N|Fs],Res) :-
  nth1(N,Is,R),
  json_get(R,Fs,Res).
json_get(Res,[],Res).

This produces Head1 not Head2 in your 2nd example. Please explain how that is supposed to work, if you did not just make a typo. (If it is zero-based you can just change nth1/3 to nth0/3.)

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