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Anonymous Struct and Union

The C programming language has anonymous structures and unions, which provide the ability to define structures and unions without specifying a name.

// Anonymous union example
union
{
    char x;
    int y;
};

// Anonymous structure example
struct
{
    char x;
    int y;
};

Since there are no names, direct objects (or variables) are not created from them we use them as nested structures or unions.

You can use anonymous structs/unions when they are nested and will only be used where they are declared.

main.c


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#include <stdio.h>

struct ASCIItable {
    // Anonymous union
    union {
        char symbol;
        int num;
    };
};

int main()
{
    struct ASCIItable AZtable;
    AZtable.num = 65;

     // number 65 is first symbol `A`,
     // number 97 is last `Z` symbol, hence 97 - 65 = 25, 
     // so 26 iterations required (including number 0)

    for (int i = 0; i < 26; i++)
        printf("x.num = %d | x.symbol = `%c`\n", AZtable.num + i, AZtable.symbol + i);

    return 0;
}

Note

Union allows the same set of bits to be represented differently depending on the context. For example, in an ASCIItable structure, you can interpret the same value as a character (using symbol) or as a numeric value (using num). This can be useful when you need to quickly switch between different data views.

Opgave

Swipe to start coding

Create an anonymous structure;
Declare three float fields in it with the names x, y, radius;
Define the fields of the structure instance;
Display the values of the structure fields.

Løsning

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Anonymous Struct and Union

The C programming language has anonymous structures and unions, which provide the ability to define structures and unions without specifying a name.

// Anonymous union example
union
{
    char x;
    int y;
};

// Anonymous structure example
struct
{
    char x;
    int y;
};

Since there are no names, direct objects (or variables) are not created from them we use them as nested structures or unions.

You can use anonymous structs/unions when they are nested and will only be used where they are declared.

main.c


              123456789101112131415161718192021222324
            
#include <stdio.h>

struct ASCIItable {
    // Anonymous union
    union {
        char symbol;
        int num;
    };
};

int main()
{
    struct ASCIItable AZtable;
    AZtable.num = 65;

     // number 65 is first symbol `A`,
     // number 97 is last `Z` symbol, hence 97 - 65 = 25, 
     // so 26 iterations required (including number 0)

    for (int i = 0; i < 26; i++)
        printf("x.num = %d | x.symbol = `%c`\n", AZtable.num + i, AZtable.symbol + i);

    return 0;
}

Note

Union allows the same set of bits to be represented differently depending on the context. For example, in an ASCIItable structure, you can interpret the same value as a character (using symbol) or as a numeric value (using num). This can be useful when you need to quickly switch between different data views.

Opgave

Swipe to start coding

Create an anonymous structure;
Declare three float fields in it with the names x, y, radius;
Define the fields of the structure instance;
Display the values of the structure fields.

Løsning

Skift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder

Var alt klart?

Tak for dine kommentarer!

Stryg for at vise menuen

Anonymous Struct and Union

Løsning

Awesome!

Anonymous Struct and Union

Løsning

Awesome!