如何访问变量的先前值？ [英] How Do I Access The Previous Values Of A Variable?

问题描述

我如何访问变量的先前值？

考虑我已经初始化了x值，如下所示：

x = 5;

然后我设置x = 10;

和第三行我设置x = 20;

如何才能访问以前的x值？

how can i access the previous values of a variable?
consider i have initialized the x value like this:
x = 5;
then i set the x = 10;
and at the third line i set the x = 20;
how can i access the previous values of x ?

推荐答案

除非您将这些先前的值存储在其他位置，否则不能。

变量包含单个值，并且不保留不同的历史记录值已被保留。

You cannot, unless you have stored these previous values elsewhere.
A variable holds a single value, and does not maintain a history of the different values is has held.

它本身不存在于C ++或C＃语言中。



做你想做的事，唯一的方法是手动构建一个记忆你的变量值的系统。



我看到的唯一实际用法是作为允许反向执行的调试器的一部分。

It doesn't exist natively in the language C++ or C#.

To do what you want, the only way is to manually build a system that memorize your variable values.

The only practical usage I see is as a part of a debugger that would allow backward execution.

你不能：内存被覆盖，以前的值丢失。

如果你需要以前的值，那么你必须明确地存储它们（例如使用集合，例如， std :: vector ，或一个普通数组。

你可以很好地将这种机制包装在你自己的'Variable'类中。

You cannot: memory is overwritten, previous values are lost.
If you need the previous values then you have to store them explicitely (e.g. using a collection, like for instance, a std::vector, or a plain array).
You may nicely wrap such a mechanism in your own 'Variable' class.

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