关于评估订单的问题 [英] Question about evaluation order

问题描述

大家好，


我对C ++中的评估顺序有一个非常具体的问题。

假设某种自定义数组类，带有超载的下标

运算符。在以下代码中：


{

my_array a，b，c;


a [6] = b [5] + c [4];

}


我会假设以下顺序：


1 ）下标运算符被评估为''b''和''c''，两者都是
返回一个引用（例如，double&）
2）调用operator，返回一个临时对象

3）下标运算符被评估为'a''，返回一个引用。

4）=运算符被计算。


我的问题：这是事情的方式，还是这个命令没有定义在

C ++中？更具体一点：a（步骤3）的下标评估是否可能已经在步骤1中完成（在添加运算符之前）？


Thanx，

Jeroen

解决方案

Jeroen写道：
< blockquote class =post_quotes>
更具体一点：a（步骤3）的下标评价是否可能已经在步骤1中完成（在此之前） add-operator）？

是的。


-


- - Pete

Roundhouse Consulting，Ltd。（ www.versatilecoding.com ）

标准C ++库扩展：教程和
参考的作者。 （ www.petebecker.com/tr1book ）

Pete Becker schreef：

Jeroen写道：

>要更多具体：是否有可能在步骤1中（在添加运算符之前）完成了对'a''（步骤3）的下标评估？

是。

谢谢皮特！这使我无法完成一个实现，即

最终不起作用....

Jeroen < no ***** @ thanx.comwrote in message news：45e57267

Hi all,

I''ve got a very specific question about the evaluation order in C++.
Assume some kind of custom array class, with an overloaded subscript
operator. In the following code:

{
my_array a, b, c;

a[6] = b[5] + c[4];
}

I would assume the following order:

1) The subscript operators are evaluated for ''b'' and ''c'', both
returning a reference (double& for example)
2) The add-operator is called, returning a temporary object
3) The subscript operator is evaluated for ''a'', returning a reference.
4) The = operator is evaluated.

My question: is this the way things go, or is this order not defined in
C++? To be more specific: is it possible that the subscript evaluation
for ''a'' (step 3) is done already in step 1 (before the add-operator)?

Thanx,

Jeroen

解决方案

Jeroen wrote:

To be more specific: is it possible that the subscript evaluation
for ''a'' (step 3) is done already in step 1 (before the add-operator)?

Yes.

--

-- Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (www.petebecker.com/tr1book)

Pete Becker schreef:

Jeroen wrote:

>To be more specific: is it possible that the subscript evaluation for
''a'' (step 3) is done already in step 1 (before the add-operator)?

Yes.

Thanks Pete! That keeps me from working out an implementation that
doesn''t work in the end....

"Jeroen" <no*****@thanx.comwrote in message news:45e57267

这篇关于关于评估订单的问题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！