两个子句定义以查找列表上的最大数 [英] Two clause definition to find the maximum number on a list

问题描述

我将如何编写两个子句递归定义来查找列表中的最大值.到目前为止，我已经写了这个:

How would I write a two clause recursive definition to find the maximum value in a list. So far I have written this:

 max(L,M):-  

 max([H|T],M):-

max(T,H,M).
max([],M,M).
max([H|T],Y,M):-
   H =< Y,
   max(T,Y,M).
max([H|T],Y,M):-
   H > Y,
   max(T,H,M).

这不起作用，它说有一个我不太清楚的语法错误，而且我知道它也不是两个子句.有谁知道我如何简化它以使其成为两个子句?

This doesn't work, it says there is a syntax error which I can't quite see, and I know it isn't two clause either. Anyone know how I could simplify it to make it two clause?

推荐答案

和你一样，我使用 'max' 名称作为谓词.此实现不依赖于任何内置谓词:

As you, I use the 'max' name for the predicate. This implementation don't rely in any built-in predicate:

max([X],X).
max([X|Xs],X):- max(Xs,Y), X >=Y.
max([X|Xs],N):- max(Xs,N), N > X.

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