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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>

typedef union { int   as_int; float as_float; char* as_string; } NumberValue;
     // └──────────────────────────────────────────────────────────────────┘
     //                  looks like a variable declaration
     //                           «TYPE» «NAME»

typedef enum {
    TYPE_UNINITIALIZED,
    TYPE_INT,
    TYPE_FLOAT,
    TYPE_STRING
} NumberType;



typedef struct {  // 'Number' will now include both the value and the type.
    NumberValue value;
//  └───────────────┘
//    «TYPE»   «NAME»

    NumberType  type;
} Number;


void print_number(Number n) {
    if(n.type == TYPE_INT) {
        printf("n has the value %d\n", n.value.as_int);
    }
    else if(n.type == TYPE_FLOAT) {
        printf("n has the value %.08f\n", n.value.as_float);
    }
    else if(n.type == TYPE_STRING) {
        printf("n has the value %s\n", n.value.as_string);
    }
}

int main(int argc, char* argv[]) {

    Number  n = { .value = { .as_int = 3 }, .type = TYPE_INT };
    print_number(n);

    n.value.as_float = 3.1415;
    n.type = TYPE_FLOAT;
    print_number(n);
    
    n.value.as_string = "e";
    n.type = TYPE_STRING;
    print_number(n);

    printf("TYPE_INT    == %d\n", TYPE_INT);
    printf("TYPE_FLOAT  == %d\n", TYPE_FLOAT);
    printf("TYPE_STRING == %d\n", TYPE_STRING);

    return EXIT_SUCCESS;
}
/* vim: set tabstop=4 shiftwidth=4 fileencoding=utf-8 noexpandtab: */

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