doubly linked list

Former Member — Mon, 26 Oct 2009 05:19:25 GMT

hello,

i want to write code for doubly linked list in sap abap. I have a problem in declaring the nodes with previous pointer and next pointer. Please help me in the code.

Thank you,

Re: doubly linked list

hubert_heitzer — Mon, 26 Oct 2009 09:21:52 GMT

Hi Aarti,

here I have an example for a double linked list:


TYPES:
  BEGIN OF lt_dllnode,
    value TYPE i,
    prev  TYPE REF TO data,
    next  TYPE REF TO data,
  END OF lt_dllnode
.

DATA:
  lr_root   TYPE REF TO lt_dllnode,
  lr_cursor TYPE REF TO lt_dllnode,
  lr_llelem TYPE REF TO lt_dllnode
.

* create a double linked list with 10 entries
CREATE DATA lr_root.
lr_root->value = 0.

lr_cursor = lr_root.
DO 9 TIMES.
  CREATE DATA lr_llelem.
  lr_llelem->value = sy-index.

  lr_cursor->next = lr_llelem.
  lr_llelem->prev = lr_cursor.
  lr_cursor = lr_llelem.
ENDDO.

* output of list values
lr_cursor = lr_root.
WHILE lr_cursor IS NOT INITIAL.

  WRITE: / lr_cursor->value.
  lr_cursor ?= lr_cursor->next.

ENDWHILE.

I think there is an ABAP keyword for recursive type definition to avoid downcast, but i dont remember.

Another alternative would be to work with ABAP objects.

Regards, Hubert

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doubly linked list

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