建立一个列表，但要注意前面的元素 [英] Build up a list, but mind the previous elements

问题描述

我遇到了以下问题:

我想从头到尾一个一个地建立一个列表.但是我有一个条件，它取决于已经插入的元素.

I want to build up a list one-by-one from head to tail. But I have a condition, which depends on the already inserted elements.

condition(Sofar, Element) :-     
    between(1, 150, Element2),  
    \+member(Element2, Sofar),
    Element = Element2.

makelist(L) :- maplist(condition(L), L).

重要提示:Sofar 不能包含 NewElement，我只是想断言！这就是我所有尝试都失败的地方，因为使用 maplist，列表中有一个引用，它获取 NewElement

An important note: Sofar must not contain NewElement, what I just try to assert! This is the point, where all my tries failed, because, with maplist, there is a reference in the list which gets the value of NewElement

当然我有更复杂的条件，但如果我能解决这个问题，那么我就可以适应它.

Of course I have more complicated conditions like this, but if I could solve this, then I could adapt it.

推荐答案

您正在尝试将您在面向命令(也称为命令式)语言中学到的概念映射到 Prolog.Sofar 或 makelist 之类的名称暗示您正在一步一步地做某事.通过描述列表的外观，尝试从另一个角度看待所有这些:

You are trying to map notions you have learned in command-oriented (a.k.a imperative) languages to Prolog. Names like Sofar or makelist imply that you are doing something step-by-step. Try to see all of this from another angle by describing how the list looks like:

1 到 150 之间的所有不同元素的列表.

A list of elements between 1 and 150 that are all different.

all_dif([]).
all_dif([E|Es]) :-
   maplist(dif(E), Es),
   all_dif(Es).

speciallist(Es) :-
   all_dif(Es),
   maplist(between(1,150), Es).

或者，使用 clpfd:

:- use_module(library(clpfd)).

specialfdlist(Es) :-
   Es ins 1..150,
   all_different(Es).

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