Kotlin是否具有身份识别功能? [英] Does Kotlin have an identity function?

问题描述

Scala在Predef中具有通用的identity函数:

Scala has a generic identity function in the Predef:

def identity[A](x: A): A

Kotlin在标准库中有类似的功能吗?当然，我可以简单地使用{ it }代替，但是我发现identity更易于阅读，并且实例化所有这些lambda有点浪费.

Does Kotlin have a similar facility in the standard library? Of course I could simply use { it } instead, but I find identity easier to read, and instantiating all those lambdas is a little wasteful.

对于任何类型的Foo，我必须能够在需要功能(Foo) -> Foo的地方使用此identity函数.这样的功能在Kotlin的字体系统中甚至可能吗? (对于Scala，存在一个隐式转换，该转换将方法包装在函数对象之内.)

I must be able to use this identity function in places where a function (Foo) -> Foo is expected, for any type Foo. Is such a function even possible in Kotlin's type system? (In the case of Scala, there is an implicit conversion that wraps the method inside a function object or something.)

推荐答案

目前尚无此功能，但您可以自己轻松定义它:

There's no such function at the moment, but you can easily define it yourself:

fun <T> identity(x: T): T = x

如果您认为有足够的用例可以在Kotlin标准库中声明此功能，请在 youtrack上提出问题. jetbrains.com .谢谢！

If you think there are enough use cases for this function to be declared in Kotlin standard library, please file an issue at youtrack.jetbrains.com. Thanks!

这篇关于Kotlin是否具有身份识别功能?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！