* META ((export #t))
function sc_filter(proc, l1) {
    var dummy = { cdr : null };
    var tail = dummy;
    while (l1 !== null) {
	if (proc(l1.car) !== false) {
	    tail.cdr = sc_cons(l1.car, null);
	    tail = tail.cdr;
	}
	l1 = l1.cdr;
    }
    return dummy.cdr;
}