Use the De Morgan rule to understand the code.

Non-functional Code Determines the quality of the Code.
Use the De Morgan rule to understand the code Category: C ++ 53 reading Comment (0) Favorites Report

Today, I am reading code reading methods and practices. I found it interesting to use Morgan's law to analyze the code. I searched it online.

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De Morgan rule:

1. ! (X & Y) →! X |! Y
2. ! (X | Y) →! X &&! Y

How can this be used?

For example, let's look at the code for finding the minimum value of a three-digit number:

2. If (x <Y & x <z)
4. Min = X;
6. Else if (Y <z)
8. Min = y;
10. Else
12. Min = z;

Many beginners (including me in the past) feel difficult to understand the above logic and always feel like nothing.

Let's take a look at the De Morgan rule,

The first if clause is used to judge x <Y & x <Z. If it is true, the minimum value is X. This is easy to understand. The key is to execute the following else if (Y <z) what are the conditions? Naturally

1. ! (X <Y & x <z) → x> = Y | x> = z

So if you run this step, it means that X must be greater than Y and Z, so it must not be the minimum value, next, you just need to judge the size of Y and Z.