code: 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;
  }
docs: * META ((export #t))