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 55 56 57 58 | #include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include "clog.h"
// Q: Can I avoid typing "struct"?
// A: Use typedef. Essentially, this creates a type with a shorter name. There's a
// derivation which will explain why this works, which I'll go over another day.
//
// struct Point { int x; int y; };
// struct Point p = { .x = 5, .y = 6};
//
// .... equivalent to ...
//
// typedef struct { int x; int y; } Point;
// Point p = { .x = 5, .y = 6};
//
// and likewise for a union or enum.
typedef struct {
union {
int as_int;
double as_double;
}; // OMIT NAME to make an anonymous union inside the struct. (C11)
// } value;
enum NumberType {
NUMBER_INT, // 0
NUMBER_DOUBLE // 1
} type; // field name is here <<<<<<
} Number;
void print_number_value(Number n) {
if(n.type == NUMBER_INT) {
printf("%d\n", n.as_int);
//printf("%d\n", n.value.as_int);
}
else if(n.type == NUMBER_DOUBLE) {
printf("%f\n", n.as_double);
//printf("%f\n", n.value.as_double);
}
}
int main(int argc, char* argv[]) {
printf("Declare and initialize n to 5 (as an int).\n");
// union NumberValue n = { .as_int = 5 };
// enum NumberType type_of_n = NUMBER_INT;
Number n = { .as_int = 5, .type = NUMBER_INT };
// print_number_value(n, type_of_n);
print_number_value(n);
return EXIT_SUCCESS;
}
/* vim: set tabstop=4 shiftwidth=4 fileencoding=utf-8 noexpandtab: */
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