forked from KolibriOS/kolibrios
184 lines
3.0 KiB
Plaintext
184 lines
3.0 KiB
Plaintext
(*
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BSD 2-Clause License
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Copyright (c) 2018, Anton Krotov
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All rights reserved.
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*)
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MODULE LISTS;
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IMPORT C := COLLECTIONS;
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TYPE
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ITEM* = POINTER TO RECORD (C.ITEM)
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prev*, next*: ITEM
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END;
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LIST* = POINTER TO RECORD
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first*, last*: ITEM
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END;
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PROCEDURE push* (list: LIST; item: ITEM);
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BEGIN
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ASSERT(list # NIL);
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ASSERT(item # NIL);
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IF list.first = NIL THEN
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list.first := item;
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list.last := item;
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item.prev := NIL;
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item.next := NIL
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ELSE
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ASSERT(list.last # NIL);
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item.prev := list.last;
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list.last.next := item;
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item.next := NIL;
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list.last := item
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END
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END push;
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PROCEDURE pop* (list: LIST): ITEM;
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VAR
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last: ITEM;
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BEGIN
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ASSERT(list # NIL);
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last := list.last;
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IF last # NIL THEN
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IF last = list.first THEN
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list.first := NIL;
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list.last := NIL
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ELSE
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list.last := last.prev;
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list.last.next := NIL
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END;
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last.next := NIL;
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last.prev := NIL
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END
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RETURN last
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END pop;
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PROCEDURE insert* (list: LIST; cur, nov: ITEM);
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VAR
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next: ITEM;
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BEGIN
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ASSERT(list # NIL);
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ASSERT(nov # NIL);
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ASSERT(cur # NIL);
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next := cur.next;
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IF next # NIL THEN
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next.prev := nov;
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nov.next := next;
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cur.next := nov;
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nov.prev := cur
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ELSE
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push(list, nov)
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END
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END insert;
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PROCEDURE insertL* (list: LIST; cur, nov: ITEM);
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VAR
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prev: ITEM;
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BEGIN
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ASSERT(list # NIL);
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ASSERT(nov # NIL);
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ASSERT(cur # NIL);
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prev := cur.prev;
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IF prev # NIL THEN
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prev.next := nov;
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nov.prev := prev;
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cur.prev := nov;
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nov.next := cur
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ELSE
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nov.prev := NIL;
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cur.prev := nov;
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nov.next := cur;
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list.first := nov
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END
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END insertL;
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PROCEDURE delete* (list: LIST; item: ITEM);
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VAR
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prev, next: ITEM;
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BEGIN
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ASSERT(list # NIL);
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ASSERT(item # NIL);
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prev := item.prev;
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next := item.next;
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IF (next # NIL) & (prev # NIL) THEN
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prev.next := next;
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next.prev := prev
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ELSIF (next = NIL) & (prev = NIL) THEN
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list.first := NIL;
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list.last := NIL
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ELSIF (next = NIL) & (prev # NIL) THEN
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prev.next := NIL;
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list.last := prev
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ELSIF (next # NIL) & (prev = NIL) THEN
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next.prev := NIL;
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list.first := next
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END
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END delete;
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PROCEDURE count* (list: LIST): INTEGER;
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VAR
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item: ITEM;
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res: INTEGER;
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BEGIN
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ASSERT(list # NIL);
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res := 0;
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item := list.first;
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WHILE item # NIL DO
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INC(res);
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item := item.next
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END
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RETURN res
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END count;
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PROCEDURE create* (list: LIST): LIST;
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BEGIN
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IF list = NIL THEN
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NEW(list)
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END;
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list.first := NIL;
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list.last := NIL
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RETURN list
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END create;
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END LISTS. |