C language custom types - Enumeration

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This time I took you to learn the definition of enumeration type 、 Advantages and use .

The next article will take you to learn about the consortium .

Catalog

enumeration

1. Definition of enumeration type

2. Advantages of enumerating types

3. Use of enumeration types

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enumeration

Enumeration actually means enumerating one by one , List the possible values one by one .

for example ：

1. From Monday to Sunday, there are 7 God , You can list them one by one .
2. Gender has male 、 A woman 、 Confidentiality can also be listed one by one .
3. Month has 12 Months , You can also list them one by one .

The value is limited .

1. Definition of enumeration type

example 1：

enum Day// week 
{
	Mon,
	Tous,
	Wed,
	Thur,
	Fri,
	Sat,
	Sun
};

struct stu
{
    int a;
    char b;
};

1. enum Is an enumeration keyword ,Day Is the tag of enumeration ;struct Is the structure keyword ,stu Is the label of the structure .
2. Both have 1 individual {} And semicolon , The structure is called member variable , Enumerations are called enumerating constants .
3. In grammatical form , Enumerations are all comma terminated , The structure is semicolon .

example 2：

enum Day// week 
{
	Mon,
	Tous,
	Wed,
	Thur,
	Fri,
	Sat,
	Sun
};

int main()
{
	enum Day d = Fri;
	return 0;
}

1. At this time d It means Friday , and d The value of can only be one of the enumeration types .
2. {} The contents are the possible values of enumeration types .

All possible values of enumeration types have values , The default from the 0 Start , One increment 1, Of course, initial values can also be assigned when defining .

example 3：

enum Day// week 
{
	Mon,//0
	Tous,//1
	Wed,//2
	Thur,//3
	Fri,//4
	Sat,//5
	Sun//6
};

int main()
{
	printf("%d\n", Mon);
	printf("%d\n", Tous);
	printf("%d\n", Wed);

	return 0;
}

Code results ：

example 4：

Modify the default value of enumeration

enum Day// week 
{
	Mon = 1,
	Tous,
	Wed,
	Thur,
	Fri,
	Sat,
	Sun
};

int main()
{
	//enum Day d = Fri;
	printf("%d\n", Mon);
	printf("%d\n", Tous);
	printf("%d\n", Wed);
	printf("%d\n", Thur);
	printf("%d\n", Fri);
	printf("%d\n", Sat);
	printf("%d\n", Sun);

	return 0;
}

Code results ：

2. Advantages of enumerating types

Why use enumeration

Advantages of enumeration ：

1. Increase the readability and maintainability of the code
2. and #define The defined identifier comparison enumeration has type checking , More rigorous
3. Prevent naming pollution （ encapsulation ）
4. Easy to debug
5. Easy to use , You can define more than one constant at a time

3. Use of enumeration types

enum Color// Color 
{
	RED = 1,
	GREEN = 2,
	BLUE = 4
};
int main()
{
	enum Color color = GREEN;// Only enumeration constants can be assigned to enumeration variables , There will be no type difference .
	color = 5; //error
	return 0;
}