应该！(Should a ! function return anything?)

应该！(Should a ! function return anything?)

在风格指南中，它表示修改其参数的函数应标有! 。 然而在给出函数double!的例子中 double! 返回修改的参数a 。 为什么要返回它，如果它已被修改？ 有必要吗？

In the style guide it says that functions that modify their arguments should be marked with a !. However in the example given the function double! returns the modified argument a. Why return it if it has already been modified? Is it necessary?

最满意答案

它不需要任何费用，并且可以让您执行以下操作：

b = double!(a)*x

要么

double!(double!(a))

如果你需要的话，可以在一行中。

出于这个原因（即方便），它已经成为惯例。

It doesn't cost anything and enables you do things like:

b = double!(a)*x

or

double!(double!(a))

in a single line if you needed to.

For that reason (i.e. convenience), it has become convention.