1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | #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: */
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