these days, some lang has array/list and hashtable mixed into one. It is popularized by php.
php started that way probably due to a hack. The lang doesn't have arrays, but what it calls array is a mix of hashtable. When used like array, the keys are automatically filled with 0, 1, 2, etc. 〔➤ PHP: Array Basics〕
though, i heard lua is also mixed array/hashtable. Anyone know if it's really good?