序言列表和过滤 [英] Prolog list and filtering

问题描述

我在Prolog练习中遇到问题.我正在尝试在家中独自学习计算机科学，并且正在做一系列从互联网上进行的练习.

I have a problem with a Prolog exercise. I'm trying to study Computer Science alone at my home, and I'm doing a series of exercises I've taken from the Internet.

问题如下；

构造一个称为 filteringPairsAtoms/3 的谓词，以便给定一个原子(第一个参数)和一个对对，通过仅选择具有以下对的对，将第三个参数与过滤后的对对统一第一个成分是第一个参数的原子.

Construct a predicate called filteringPairsAtoms/3 so that given an atom (first argument), and a list of pairs, unify a third parameter with the filtered list of pairs by selecting only the pairs that have the first component as the atom of the first argument.

示例

filteringPairsAtoms(sA,[[basA,absAb],[ab,bbsA],[sA,abbsB],[bsA,sAsB],[sA,bb]],X)  

必须导致

X = [[sA,abbsB],[sA,bb]]

我正在尝试解决问题，但是我没有人要问，因为我一个人学习，也没有教授写东西.

I'm trying to solve it but I don't have anyone to ask, because I'm learning alone, and don't have a professor to write to or something.

欢迎任何帮助.

谢谢！

推荐答案

您可以从已有的内容开始:

You can start from what you already have:

filteringPairsAtoms(sA, [[basA,absAb],[ab,bbsA],[sA,abbsB],[bsA,sAsB],[sA,bb]], X) :-
    X = [[sA,abbsB],[sA,bb]].

这是一个很好的开始.但是我们知道更多:肯定是这种情况

That's as good a start as any. But we know more: it must be the case that

filteringPairsAtoms(sA, [[sA,abbsB],[bsA,sAsB],[sA,bb]], X) :-
    X = [[sA,abbsB],[sA,bb]].

%% and
filteringPairsAtoms(sA, [[bsA,sAsB],[sA,bb]], X) :-
    X = [[sA,bb]].

%% and
filteringPairsAtoms(sA, [[sA,bb]], X) :-
    X = [[sA,bb]].

%% and
filteringPairsAtoms(sA, [], X) :-
    X = [].

比较顺序子句，我们还注意到它必须是

Comparing the sequential clauses, we also notice that it must be

filteringPairsAtoms(sA, [[sA,abbsB] | [[bsA,sAsB],[sA,bb]] ], X) :-
    sA = sA,
    X = [[sA,abbsB] | Y],
    filteringPairsAtoms(sA, [[bsA,sAsB],[sA,bb]], Y).

(这只是上面的前两个子句的总和)；和

(this is just the first two clauses from above, combined); and

filteringPairsAtoms(sA, [[bsA,sAsB] | [[sA,bb]] ], X) :-
    dif( sA, bsA),
    X = Y,
    filteringPairsAtoms(sA, [[sA,bb]], Y).

剩下要做的就是通过用逻辑变量替换具体术语来概括.像这样:

All that's left for you to do, is generalize this by replacing concrete terms with logical variables. Like this:

filteringPairsAtoms(SA, [Head | Tail ], X) :-
    Head = [BsA, _]
    dif( SA, BsA),
    X = Y,
    filteringPairsAtoms(SA, Tail, Y).

，并将其完全执行到最后.

and carry this out fully to the end.

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