const func integer: binarySearch (in array elemType: arr, in elemType: aKey, in integer: low, in integer: high) is func
  result
    var integer: result is 0;
  begin
    if low <= high then
      result := (low + high) div 2;
      if aKey < arr[result] then
        result := binarySearch(arr, aKey, low, pred(result)); # search left
      elsif aKey > arr[result] then
        result := binarySearch(arr, aKey, succ(result), high); # search right
      end if;
    end if;
  end func;

const func integer: binarySearchRecursive (in array elemType: arr, in elemType: aKey) is
  return binarySearch(arr, aKey, 1, length(arr));