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