test/t53_funcptr.nsc

/* function pointers: &name takes a function's address (a plain ptr),
 * and calling a ptr value is an indirect call. a small dispatch table
 * picks an op by index; every result is distinct, so the exit code
 * proves the RIGHT function ran each time. */
i32 add(i32 a, i32 b) { return a + b; }
i32 sub(i32 a, i32 b) { return a - b; }
i32 mul(i32 a, i32 b) { return a * b; }
i64 hits = 0;
void bump(void) { hits = hits + 1; }
ptr pick(ptr a, ptr b, i32 which) {
	if (which) { return a; }
	return b;
}
 
struct ops { ptr fn; i32 bias; };
 
global i32 main(void) {
	ptr tbl[3];
	tbl[0] = &add;
	tbl[1] = ⊂
	tbl[2] = &mul;
	i32 acc = 0;
	i32 i = 0;
	/* (7+3) + (7-3) + (7*3) = 10 + 4 + 21 = 35 */
	while (i < 3) {
		acc = acc + (i32)tbl[i](7, 3);
		i++;
	}
	/* a plain ptr variable, called by its bare name */
	ptr f = &mul;
	acc = acc + (i32)f(2, 5);           /* 45 */
	/* a call through a ptr returned by a call */
	acc = acc + (i32)pick(&sub, &add, 1)(9, 4);   /* sub: 50 */
	/* a statement-level indirect call to a void function */
	ptr g = &bump;
	g();
	g();
	/* through a struct field */
	struct ops o;
	o.fn = &add;
	o.bias = 1;
	acc = acc + (i32)o.fn(o.bias, 1);   /* 52 */
	/* function addresses compare like any other ptr */
	if (tbl[2] == f) { acc = acc + 1; }  /* 53 */
	if (tbl[0] != f) { acc = acc + 1; }  /* 54 */
	return acc + (i32)hits;              /* 56 */
}