Prolog中偶数的总和，奇数的乘积 [英] Sum of even, product of odd numbers in Prolog

问题描述

我有一个数字列表，我需要计算列表的偶数和同一个列表的奇数的乘积.我是 Prolog 的新手，到目前为止我的搜索并不成功.谁能帮我解决一下?

I have a list of numbers, I need to calculate the sum of the even numbers of the list and the product of the odd numbers of the same list. I'm new in Prolog, and my searches so far weren't successful. Can anyone help me solve it ?

l_odd_even([]). 
l_odd_even([H|T], Odd, [H|Etail]) :-
    H rem 2 =:=0,
    split(T, Odd, Etail). 
l_odd_even([H|T], [H|Otail], Even) :-
    H rem 2 =:=1,
    split(T, Otail, Even).

推荐答案

这里是一个列表中偶数和的建议:

Here is a suggestion for the sum of the even numbers from a list:

even(X) :- 
  Y is mod(X,2),       % using "is" to evaluate to number
  Y =:= 0.

odd(X) :-              % using even
  Y is X + 1,
  even(Y).

sum_even(0, []).       % empty list has zero sum
sum_even(X, [H|T]) :- 
  even(H),
  sum_even(Y, T), 
  X is Y+H.
sum_even(X, [H|T]) :- 
  odd(H),
  sum_even(X, T).      % ignore the odd numbers

注意:我的 Prolog 已氧化，因此可能有更好的解决方案.:-)

Note: My Prolog has oxidized, so there might be better solutions. :-)

注意:圣牛！语法高亮似乎没有 Prolog 支持(请参阅 这里)，所以我使用了 Erlang 语法.哈，确实有效.:-)

Note: Holy cow! There seems to be no Prolog support for syntax highlighting (see here), so I used Erlang syntax. Ha, it really works. :-)

在 GNU Prolog 中运行一些查询，我得到:

Running some queries in GNU Prolog, I get:

| ?- sum_even(X,[]).    
X = 0 ?     
yes

| ?- sum_even(X,[2]).   
X = 2 ? 
yes

| ?- sum_even(X,[3]).    
X = 0 ? 
yes

| ?- sum_even(X,[5,4,3,2,1,0]).    
X = 6 ? 
yes

这里应用的想法应该使您能够提出所需的产品.

The ideas applied here should enable you to come up with the needed product.

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