// this could be made quite a bit faster with realloc

Arr ::= struct (t :: Type) {
	data : []t;
	cap : int;
};

resv ::= fn(t ::=, a : &Arr(t), n: int) {
	if a.cap >= n {
		return;
	}
	a.cap = n;
	new_data := new(t, a.cap);
	new_data.len = a.data.len;
	for x, i := &new_data {
		*x = a.data[i];
	}
	a.data = new_data;
};

add ::= fn(t ::=, a : &Arr(t), x : t) {
	if a.data.len >= a.cap {
		resv(a, a.cap * 2 + 2);
	}
	a.data.len += 1;
	a.data[a.data.len-1] = x;
};

len ::= fn(t ::=, a : Arr(t)) int { a.data.len };