Question

How to declare, initialize and print a union and an enum inside a struct in C

Answer 1

#include <stdio.h>

struct enum_union
{
    enum { A, B } enm;
    union
    {
        int   i;
        float f;
    } uni;
};

int main(void) 
{
    struct enum_union enm_uni1 = { .enm = A, .uni = { .i = 1 } };
    
    printf("%d %.2f\n", enm_uni1.uni.i, enm_uni1.uni.f);
    printf("%d %d\n", A, B);
  
    return 0;
}
    
/*
run:
 
1 0.00
0 1

*/

 

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Answer 2

#include <stdio.h>

struct enum_union
{
    enum { A, B } enm;
    union
    {
        int   i;
        float f;
    } uni;
};

int main(void) 
{
    struct enum_union enm_uni1 = { .uni = { .f = 3.14 } };
    
    printf("%d %.2f\n", enm_uni1.uni.i, enm_uni1.uni.f);
    printf("%d %d\n", A, B);
  
    return 0;
}
    
/*
run:
 
1078523331 3.14
0 1

*/

 

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Answer 3

#include <stdio.h>

struct enum_union
{
    enum { A = 3, B } enm;
    union
    {
        int   i;
        float f;
    } uni;
};

int main(void) 
{
    struct enum_union enm_uni1 = { .uni = { .i = B } };
    
    printf("%d %.2f\n", enm_uni1.uni.i, enm_uni1.uni.f);
    printf("%d %d\n", A, B);
  
    return 0;
}
    
/*
run:
 
4 0.00
3 4

*/

 

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