Scala 的 += 在 Int 的上下文中定义在哪里? [英] Where is Scala's += defined in the context of Int?

问题描述

刚开始使用 Scala
var c = 0
c += 1 有效
c.+= 给我 error: value += is not a member of Int

Just starting out with Scala
var c = 0
c += 1 works
c.+= gives me error: value += is not a member of Int

+= 在哪里定义的?

推荐答案

Scala 语言规范 (SLS) 的第 6.12.4 节赋值运算符解释了如何对此类复合赋值运算符进行脱糖:

Section 6.12.4 Assignment Operators of the Scala Language Specification (SLS) explains how such compound assignment operators are desugared:

l ω= r

(其中 ω 是除 <、>、! 和不以 = 开头)被脱糖为

(where ω is any sequence of operator characters other than <, >, ! and doesn't start with =) gets desugared to

l.ω=(r)

IFF l 具有名为 ω= 的成员，或者可以隐式转换为具有名为 ω=<的成员的对象/代码>.

IFF l has a member named ω= or is implicitly convertible to an object that has a member named ω=.

否则，它会被脱糖

l = l.ω(r)

(除了 l 保证只被评估一次)，如果类型检查.

(except l is guaranteed to be only evaluated once), if that typechecks.

或者，更简单地说:编译器将首先尝试 l.ω=(r)，如果这不起作用，它将尝试 l = l.ω(r).

Or, to put it more simply: the compiler will first try l.ω=(r) and if that doesn't work, it will try l = l.ω(r).

这允许诸如 += 之类的东西像在其他语言中一样工作，但仍然被覆盖以做不同的事情.

This allows something like += to work like it does in other languages but still be overridden to do something different.

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