用比较器语法进行常规排序 [英] groovy sort with comparator syntax

问题描述

我正在用gremlin弄湿我的脚。我知道gremlin是基于groovy的。我发现这里的文档 < a>，但我仍然不确定语法是什么意思。

对于比较器的排序语法如何工作，我有点困惑：

  m.sort {a，b  - > a.value => b.value} 
  

有人可以解释 { 和} 是什么意思？ 当> Closure 被使用时排序 有两个参数，它像一个传统的 比较 。也就是说，对于在排序过程中进行的每个比较，在两个元素 a 和 b 之间进行比较，返回一个负整数，零或一个正整数，因为第一个参数小于，等于或大于第二个。

在您的特定场景中，比较结果是使用太空船运营商 < = > 。换句话说，您正在按升序顺序排列元素。

例如，如果您有列表<$ c $> [3，2，1] ，使用该排序的结果将 m.sort {a，b - > a.value => b.value} 大致等于使用下面的 compare 函数：

  int compare（a，b）{
 if（a< b）{
 return -1; 
} else else if（a> b）{
 return 1; 
} else {
 return 0; 
} 
} 
  

I am just getting my feet wet with gremlin. I understand that gremlin is based on groovy. I found the documentation here, but I am still not sure what the syntax means.

I am a bit confused as to how the syntax of sort with a comparator works:

m.sort{a,b -> a.value <=> b.value}

Could someone explain what all the different bits between the { and } mean?

解决方案

When the Closure used by sort has two parameters, it acts like a traditional Comparator. That is, for each comparison that is done during the sort, between two elements a and b, it returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

In your particular scenario, the comparison is the result of using the spaceship operator <=>. In other words, you are effectively sorting your elements in ascending order.

For example, if you had the list [ 3, 2, 1 ], the result of using that sort would be [ 1, 2, 3 ].

Thus, m.sort{a,b -> a.value <=> b.value} is roughly the equivalent of using the following compare function:

int compare(a, b) {
  if (a < b) {
    return -1;
  } else if (a > b) {
    return 1;
  } else {
    return 0;
  }
}

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