为什么在predsort上出现存在错误? [英] Why am I getting an existence error on predsort?

问题描述

我试图按完成路径所需的距离对路径列表进行排序.我正在使用的Prolog代码如下.

I am trying to sort a list of paths by the distance it takes to complete them. The Prolog code I'm using is below.

当我呼叫sortRoutes时，我从Prolog收到一个存在错误，说predsort不存在.但是，我使用的是sort模块，而且似乎没有任何改变.

When I call sortRoutes, I get an existence error from Prolog saying that predsort doesn't exist. However, I am using the sort module and that doesn't seem to change anything.

我似乎无法弄清楚为什么它不起作用.我做错什么了吗?

I can't seem to figure out why this isn't working. Am I doing anything wrong?

谢谢！

:- use_module(library(sort)).

sortRoutes(DistRoutes, SortedRoutes) :-
    predsort(distCompare, DistRoutes, SortedRoutes).

distCompare(Comp, E1, E2) :-
    my_nth(2, E1, Dist1),
    my_nth(2, E2, Dist2),
    compDists(Dist1, Dist2).

compDists(>, Dist1, Dist2) :-
    Dist1 > Dist2.
compDists(<, Dist1, Dist2) :-
    Dist1 =< Dist2.

推荐答案

我认为distCompare应该是

I think distCompare should be

distCompare(Comp, E1, E2) :-
    my_nth(2, E1, Dist1),
    my_nth(2, E2, Dist2),
    compDists(Comp, Dist1, Dist2).

这篇关于为什么在predsort上出现存在错误?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！