在Scala中，`println(1,2)`是如何工作的? [英] In Scala, how come `println(1,2)` works?

问题描述

在Scala(2.7.7final)中，Predef.println方法被定义为具有以下签名:

In Scala (2.7.7final), the Predef.println method is defined as having the following signature:

def println (x : Any) : Unit

为什么会出现以下情况?

How come, then that the following works:

scala> println(1,2)  
(1,2)

编译器是否自动将逗号分隔的参数列表转换为元组?通过什么魔术?在这里进行隐式转换吗?如果是的话，是哪一个?

Does the compiler automatically convert a comma-separated list of arguments into a Tuple? By what magic? Is there an implicit conversion going on here, and if so, which one?

推荐答案

是的，如果没有合适的多参数方法和一个合适的单参数方法，编译器将尝试将逗号分隔的参数转换为元组.这不是隐式转换，只是编译器hack.这是一个有争议的功能，随着计划围绕统一元组和参数列表的处理而开展的工作，它可能会发生变化.

Yes, the compiler will attempt to convert comma separated arguments into tuples, if there are no appropriate multi-argument methods and a single appropriate one-argument method. It's not an implicit conversion, just a compiler hack. This is a somewhat controversial feature, and will probably undergo changes going forward, as work is planned around unifying the treatment of tuples and argument lists.

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