什么时候最好使用一个数组，而不是在Perl散列？ [英] When is it better to use an array instead of a hash in Perl?

问题描述

假设你有一个数组 @a = QW / A B C D /;

和哈希％A =（'A'=大于1，'B'=大于1，'C'=＆GT; 1，'D'=＆GT; 1）;

是否有任何情况下创建阵列版本比创建哈希值（当你有其他比对所有的值进行迭代在类似

更好

 为（@a）{
    ....
 

在这种情况下，你将不得不使用键％A 如果您使用的哈希去）？因为测试的特定值是否是在哈希总是比在阵列，正确？

这样做更有效

解决方案

1. ＆＃X20;

   
   
   • 阵列是由数字索引。
   
   
   • 哈希通过字符串关键字。
   
   



2. ＆＃X20;

   
   
   • 到最高指数各项指标在数组中存在。
   
   
   • 哈希索引稀疏。 （例如，一和c可以不b的存在。）
   
   

有很多新兴的性能。首先，

1. ＆＃X20;

   
   
   • 阵列可用于存储有序列表。
   
   
   • 这将是丑陋的低效使用哈希这种方式。
   
   



2. ＆＃X20;

   
   
   • 这是不可能从数组中删除一个元素，除非它是最高的索引元素。
   
   
   • 您可以从一个有序列表中删除使用实现了一个数组，虽然它是低效率的，除去比第一或最后一个其他元素。
   
   
   • 这是可能的，从一个哈希删除一个元素，它的效率更高。
   
   

Say you have an array @a = qw/ a b c d/;

and a hash %a = ('a' => 1, 'b' => 1, 'c' => 1, 'd' => 1);

Is there any situation where creating the array version is better than creating the hash (other than when you have to iterate over all the values as in something like

for (@a){
    ....

in which case you would have to use keys %a if you went with the hash)? Because testing whether a specific value is in a hash is always more efficient than doing so in an array, correct?

解决方案

1. • Arrays are indexed by numbers.
   • Hashes are keyed by strings.

2. • All indexes up to the highest index exist in an array.
   • Hashes are sparsely indexed. (e.g. "a" and "c" can exist without "b".)

There are many emergent properties. Primarily,

1. • Arrays can be used to store ordered lists.
   • It would be ugly an inefficient to use hashes that way.

2. • It's not possible to delete an element from an array unless it's the highest indexed element.
   • You can delete from an ordered list implemented using an array, though it is inefficient to remove elements other than the first or last.
   • It's possible to delete an element from a hash, and it's efficient.

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