Used by Array#at and String#at
function entryAtIndex(arr, args, str) {
    var result = [], length = arr.length, loop = args[args.length - 1] !== false, r;
    multiArgs(args, function(index) {
      if(isBoolean(index)) return false;
      if(loop) {
        index = index % length;
        if(index < 0) index = length + index;
      }
      r = str ? arr.charAt(index) || '' : arr[index];
      result.push(r);
    });
    return result.length < 2 ? result[0] : result;
  }