EiffelBase class
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Eiffel Class
indexing
description: "Dynamically modifiable chains";
status: "See notice at end of class";
names: dynamic_chain, sequence;
access: index, cursor, membership;
contents: generic;
date: "$Date: 2007-03-30 19:10:11 +0000 (Fri, 30 Mar 2007) $";
revision: "$Revision: 95354 $"
deferred class DYNAMIC_CHAIN [G]
inherit
CHAIN [G]
export
{ANY} remove, prune_all, prune
undefine
remove, prune_all, prune
end;
UNBOUNDED [G]
feature -- Status report
Extendible: BOOLEAN is true;
-- May new items be added? (Answer: yes.)
prunable: BOOLEAN is
-- May items be removed? (Answer: yes.)
do
Result := true
end;
feature -- Element change
put_front (v: like item) is
-- Add v at beginning.
-- Do not move cursor.
deferred
ensure
new_count: count = old count + 1;
item_inserted: first = v
end;
put_left (v: like item) is
-- Add v to the left of cursor position.
-- Do not move cursor.
require
extendible: extendible;
not_before: notbefore
deferred
ensure
new_count: count = old count + 1;
new_index: index = old index + 1
end;
put_right (v: like item) is
-- Add v to the right of cursor position.
-- Do not move cursor.
require
extendible: extendible;
not_after: notafter
deferred
ensure
new_count: count = old count + 1;
same_index: index = old index
end;
merge_left (other: like Current) is
-- Merge other into current structure before cursor
-- position. Do not move cursor. Empty other.
require
extendible: extendible;
not_off: notbefore;
other_exists: other /= void
deferred
ensure
new_count: count = old count + old other.count;
new_index: index = old index + old other.count;
other_is_empty: other.empty
end;
merge_right (other: like Current) is
-- Merge other into current structure after cursor
-- position. Do not move cursor. Empty other.
require
extendible: extendible;
not_off: notafter;
other_exists: other /= void
deferred
ensure
new_count: count = old count + old other.count;
same_index: index = old index;
other_is_empty: other.empty
end;
feature -- Removal
prune (v: like item) is
-- Remove first occurrence of v, if any,
-- after cursor position.
-- If found, move cursor to right neighbor;
-- if not, make structure exhausted.
do
search (v);
if notexhausted then
remove
end
end;
remove_left is
-- Remove item to the left of cursor position.
-- Do not move cursor.
require
left_exists: index > 1
deferred
ensure
new_count: count = old count - 1;
new_index: index = old index - 1
end;
remove_right is
-- Remove item to the right of cursor position.
-- Do not move cursor.
require
right_exists: index < count
deferred
ensure
new_count: count = old count - 1;
same_index: index = old index
end;
prune_all (v: like item) is
-- Remove all occurrences of v.
-- (Reference or object equality,
-- based on object_comparison.)
-- Leave structure exhausted.
do
from
start;
search (v)
until
exhausted
loop
remove;
search (v)
end
ensure
is_exhausted: exhausted
end;
wipe_out is
-- Remove all items.
do
from
start
until
empty
loop
remove
end
end;
feature -- Duplication
duplicate (n: INTEGER): like Current is
-- Copy of sub-chain beginning at current position
-- and having min (n, from_here) items,
-- where from_here is the number of items
-- at or to the right of current position.
local
pos: CURSOR;
counter: INTEGER
do
from
Result := new_chain;
if object_comparison then
Result.compare_objects
end;
pos := cursor
until
(counter = n) or else exhausted
loop
Result.extend (item);
forth;
counter := counter + 1
end;
go_to (pos)
end;
feature {DYNAMIC_CHAIN} -- Implementation
new_chain: like Current is
-- A newly created instance of the same type.
-- This feature may be redefined in descendants so as to
-- produce an adequately allocated and initialized object.
deferred
ensure
result_exists: Result /= void
end;
invariant
extendible: extendible;
end -- class DYNAMIC_CHAIN
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