如何从具有 2 个元素的子列表中添加元素(第一个元素是字符串，第二个元素是数字)? [英] How to add elements from sublists with 2 elements (the first element is a string and the second one a number)?

问题描述

我正在处理一个包含子列表的列表，每个子列表有 2 个元素.每个子列表的第一个元素是一个字符串，第二个元素是一个数字.

I'm working on a list that contains sublists with 2 elements each. The first element of each sublist is a string and the second one a number.

[ [e, 30], [a, 170], [k, 15], [e, 50] ] 

我想添加每个子列表的所有数字.我试过这个:

I want to add all the numbers of each sublist. I tried this one:

sum_fire([H|T],S):-
  flatten(H,L),
  sum_fire(T,S),
  L=[_H1|T1],
  sum(T1,S).

但我认为这是完全错误的.我怎样才能让它工作?

but it's completely wrong, I think. How can i get this to work?

推荐答案

你只需要将字符串与数字分开:

You just need to break out the string versus the number:

sum_fire( [[_,N]|Tail], Sum ) :-
    sum_fire( Tail, S1 ),
    Sum is N + S1.
sum_fire( [], 0 ).

所以我使用 [_,N] 而不是 H 作为头部项目，因为我想要里面的东西(数字 N).我不关心和的字符串，所以它是 _.

So I'm using [_,N] instead of H for the head item because I want what's inside (the number N). I don't care about the string for the sum, so it's _.

这篇关于如何从具有 2 个元素的子列表中添加元素(第一个元素是字符串，第二个元素是数字)?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！