xcode – Swift playground打印括号

Xcode 7.2, Swift 2.0：
下面的代码在调试区域中打印“15()”.我原以为它打印“15 1”.为什么要打印括号？

var n = 15
print(n, n /= 10)

因为赋值运算符没有返回任何内容.
它仍然执行.

请参阅此处的文档：Swift Docs

The assignment operator (=) does not return a value, to prevent it from being mistakenly used when the equal to operator (==) is intended.