Doubly-linked list/Element definition: Difference between revisions

=={{header|J}}==

As discussed in [[Doubly-linked_list/Definition#J]], doubly linked lists are antithetical to J's design. Defining individual elements as independent structures is even worse. Now each element of the list must contain three arrays (everything in J is an array), all so that we can implement a list.

Yo Dawg, we heard you like lists, so we put lists in your lists so you can list while you list.

Nevertheless, this is doable, though it necessarily departs from the definition specified at [[Doubly-linked_list/Definition#J]].

coclass'DoublyLinkedListElement'

create=:3 :0

this=:coname''

'predecessor successor data'=:y

successor__predecessor=: predecessor__successor=: this

)

Here, when we create a new list element, we need to specify its successor node and its predecessor node and the data to be stored in the node. To start a new list we will need a node that can be the head and the tail of the list -- this will be the successor node for the last element of the list and the predecessor node for the first element of the list:

coclass'DoublyLinkedListHead'

create=:3 :0

predecessor=:successor=:this=: coname''

)