为什么在Scala中不赞成使用List的+运算符? [英] Why is the + operator for List deprecated in Scala?

问题描述

为什么在Scala中不建议使用List的+运算符?

Why is the + operator for List deprecated in Scala?

http://www .scala-lang.org/docu/files/api/scala/List.html#％2B％28B％29

推荐答案

很好的问题，所以我在Odersky等人的书中进行了查找.它说以下内容(希望在这里引用它不是侵犯版权；-)):

Good question, so I looked it up in the book by Odersky et al. It says the following (hopefully it's not a copyright infringement to quote this here ;-)):

类List不提供追加操作，因为追加到列表所需的时间随列表的大小线性增长，而加上::则需要固定的时间.如果您想通过添加元素来构建列表，则可以选择将它们放在前面，然后在完成后调用reverse；否则，请执行以下步骤.或使用ListBuffer(确实提供附加操作的可变列表)，并在完成后调用toList.

Class Listdoes not offer an append operation because the time it takes to append to a list grows linearly with the size of the list, whereas prepending with :: takes constant time. Your options if you want to build a list by appending elements is to prepend them, then when you're done call reverse; or use a ListBuffer, a mutable list that does offer an append operation, and when you're done call toList.

据我了解FP，至少在纯函数语言中，在列表之前添加列表比添加列表更为常见.我只能假定Scala的设计者添加了+运算符，以方便Java开发人员，因为他们习惯于使用add()进行追加，然后对此有了新的想法.

As far as I understand FP, prepending to a list is much more common than appending, at least in pure functional languages. I can only assume that the designers of Scala added the + operator as a convenience for Java developers, who are used to appending using add(), and then had second thoughts about it.

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