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

// Q: Passing around the number's union object (value) and type is cumbersome.  Why can't
//    I just use one variable.  Where's the encapulation???
// A: Use a struct to refer to multiple values of different types and roles by one name.

union NumberValue {
    int    as_int;
    double as_double;
};   // <<<< SEMICOLON!!! <<<<<

enum NumberType {
    NUMBER_INT,
    NUMBER_DOUBLE
};   // << SEMICOLON <<

struct Number {
    union NumberValue value;
    enum NumberType type;
    char* name;
};   // << SEMICOLON <<

void print_number(struct Number n) {
    if(n.type == NUMBER_INT) {
        printf("%d\n", n.value.as_int);
    }
    else if(n.type == NUMBER_DOUBLE) {
        printf("%f\n", n.value.as_double);
    }
    else {
        assert(false);  // Unexpected value of type_of_n
    }
}

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

    /* union NumberValue n = { .as_double = 654321.123456 }; */
    /* enum NumberType type_of_n = NUMBER_DOUBLE; */

    union NumberValue value_of_n = { .as_int = 5 };
    enum  NumberType  type_of_n  = NUMBER_INT;
    struct Number n = { .value = value_of_n,
                        .type  = type_of_n,
                        .name  = "Eff Eye Vee Yee" };

    //print_number(n, type_of_n);
    print_number(n);  // Value and type are now encapulated in one variable.

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