* META ((export #t))
function sc_filterBang(proc, l1) {
    var head = sc_cons("dummy", l1);
    var it = head;
    var next = l1;
    while (next !== null) {
        if (proc(next.car) !== false) {
	    it.cdr = next
	    it = next;
	}
	next = next.cdr;
    }
    it.cdr = null;
    return head.cdr;
}