indexing
description: "Dynamically modifiable chains"
names: dynamic_chain, sequence
access: index, cursor, membership
contents: generic
deferred class interface
DYNAMIC_CHAIN [G]
feature -- Access
cursor: CURSOR
-- Current cursor position
-- (from CURSOR_STRUCTURE)
first: like item
-- Item at first position
-- (from CHAIN)
require -- from CHAIN
not_empty: not empty
has (v: like item): BOOLEAN
-- Does chain include v?
-- (Reference or object equality,
-- based on object_comparison.)
-- (from CHAIN)
ensure -- from CONTAINER
not_found_in_empty: Result implies not empty
i_th (i: INTEGER): like item
-- Item at i-th position
-- Was declared in CHAIN as synonym of i_th and @.
-- (from CHAIN)
require -- from TABLE
valid_key: valid_index (k)
index: INTEGER
-- Current cursor index
-- (from CHAIN)
index_of (v: like item; i: INTEGER): INTEGER
-- Index of i-th occurrence of item identical to v.
-- (Reference or object equality,
-- based on object_comparison.)
-- 0 if none.
-- (from CHAIN)
require -- from LINEAR
positive_occurrences: i > 0
ensure -- from LINEAR
non_negative_result: Result >= 0
item: G
-- Item at current position
-- (from TRAVERSABLE)
require -- from ACTIVE
readable: readable
require -- from TRAVERSABLE
not_off: not off
require -- from TRAVERSABLE
not_off: not off
last: like item
-- Item at last position
-- (from CHAIN)
require -- from CHAIN
not_empty: not empty
occurrences (v: like item): INTEGER
-- Number of times v appears.
-- (Reference or object equality,
-- based on object_comparison.)
-- (from CHAIN)
ensure -- from BAG
non_negative_occurrences: Result >= 0
sequential_occurrences (v: G): INTEGER
-- Number of times v appears.
-- (Reference or object equality,
-- based on object_comparison.)
-- (from LINEAR)
ensure -- from BAG
non_negative_occurrences: Result >= 0
occurrences (v: like item): INTEGER
-- Number of times v appears.
-- (Reference or object equality,
-- based on object_comparison.)
-- (from CHAIN)
ensure -- from BAG
non_negative_occurrences: Result >= 0
infix "@" (i: INTEGER): like item
-- Item at i-th position
-- Was declared in CHAIN as synonym of i_th and @.
-- (from CHAIN)
require -- from TABLE
valid_key: valid_index (k)
feature -- Measurement
count: INTEGER
-- Number of items
-- (from FINITE)
feature -- Status report
after: BOOLEAN
-- Is there no valid position to the right of current one?
-- (from LINEAR)
changeable_comparison_criterion: BOOLEAN
-- May object_comparison be changed?
-- (Answer: yes by default.)
-- (from CONTAINER)
empty: BOOLEAN
-- Is structure empty?
-- (from FINITE)
exhausted: BOOLEAN
-- Has structure been completely explored?
-- (from LINEAR)
ensure -- from LINEAR
exhausted_when_off: off implies Result
Extendible: BOOLEAN is true
-- May new items be added? (Answer: yes.)
full: BOOLEAN
-- Is structure filled to capacity?
-- (from BOX)
isfirst: BOOLEAN
-- Is cursor at first position?
-- (from CHAIN)
ensure -- from CHAIN
valid_position: Result implies not empty
islast: BOOLEAN
-- Is cursor at last position?
-- (from CHAIN)
ensure -- from CHAIN
valid_position: Result implies not empty
object_comparison: BOOLEAN
-- Must search operations use equal rather than =
-- for comparing references? (Default: no, use =.)
-- (from CONTAINER)
off: BOOLEAN
-- Is there no current item?
-- (from CHAIN)
prunable: BOOLEAN
-- May items be removed? (Answer: yes.)
readable: BOOLEAN
-- Is there a current item that may be read?
-- (from SEQUENCE)
valid_cursor (p: CURSOR): BOOLEAN
-- Can the cursor be moved to position p?
-- (from CURSOR_STRUCTURE)
valid_cursor_index (i: INTEGER): BOOLEAN
-- Is i correctly bounded for cursor movement?
-- (from CHAIN)
ensure -- from CHAIN
valid_cursor_index_definition: Result = ((i >= 0) and (i <= count + 1))
valid_index (i: INTEGER): BOOLEAN
-- Is i within allowable bounds?
-- (from CHAIN)
ensure then -- from CHAIN
valid_index_definition: Result = ((i >= 1) and (i <= count))
writable: BOOLEAN
-- Is there a current item that may be modified?
-- (from SEQUENCE)
feature -- Status setting
compare_objects
-- Ensure that future search operations will use equal
-- rather than = for comparing references.
-- (from CONTAINER)
require -- from CONTAINER
changeable_comparison_criterion
ensure -- from CONTAINER
object_comparison
compare_references
-- Ensure that future search operations will use =
-- rather than equal for comparing references.
-- (from CONTAINER)
require -- from CONTAINER
changeable_comparison_criterion
ensure -- from CONTAINER
reference_comparison: not object_comparison
feature -- Cursor movement
back
-- Move to previous position.
-- (from BILINEAR)
require -- from BILINEAR
not_before: not before
require -- from BILINEAR
not_before: not before
ensure then -- from BILINEAR
moved_back: index = old index - 1
ensure then -- from BILINEAR
moved_back: index = old index - 1
before: BOOLEAN
-- Is there no valid position to the left of current one?
-- (from BILINEAR)
finish
-- Move cursor to last position.
-- (No effect if empty)
-- (from CHAIN)
ensure then -- from CHAIN
at_last: not empty implies islast
forth
-- Move to next position; if no next position,
-- ensure that exhausted will be true.
-- (from LINEAR)
require -- from LINEAR
not_after: not after
require -- from LINEAR
not_after: not after
go_i_th (i: INTEGER)
-- Move cursor to i-th position.
-- (from CHAIN)
require -- from CHAIN
valid_cursor_index: valid_cursor_index (i)
ensure -- from CHAIN
position_expected: index = i
go_to (p: CURSOR)
-- Move cursor to position p.
-- (from CURSOR_STRUCTURE)
require -- from CURSOR_STRUCTURE
cursor_position_valid: valid_cursor (p)
move (i: INTEGER)
-- Move cursor i positions. The cursor
-- may end up off if the absolute value of i
-- is too big.
-- (from CHAIN)
ensure -- from CHAIN
too_far_right: (old index + i > count) implies exhausted;
too_far_left: (old index + i < 1) implies exhausted;
expected_index: (not exhausted) implies (index = old index + i)
search (v: like item)
-- Move to first position (at or after current
-- position) where item and v are equal.
-- If structure does not include v ensure that
-- exhausted will be true.
-- (Reference or object equality,
-- based on object_comparison.)
-- (from BILINEAR)
ensure -- from LINEAR
object_found: (not exhausted and object_comparison) implies equal (v, item);
item_found: (not exhausted and not object_comparison) implies v = item
start
-- Move cursor to first position.
-- (No effect if empty)
-- (from CHAIN)
ensure then -- from CHAIN
at_first: not empty implies isfirst
feature -- Element change
append (s: SEQUENCE [G])
-- Append a copy of s.
-- (from SEQUENCE)
require -- from SEQUENCE
argument_not_void: s /= void
ensure -- from SEQUENCE
new_count: count >= old count
extend (v: G)
-- Add a new occurrence of v.
-- (from BAG)
require -- from COLLECTION
extendible: extendible
ensure -- from COLLECTION
item_inserted: has (v)
ensure then -- from BAG
one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
ensure then -- from BAG
one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
fill (other: CONTAINER [G])
-- Fill with as many items of other as possible.
-- The representations of other and current structure
-- need not be the same.
-- (from COLLECTION)
require -- from COLLECTION
other_not_void: other /= void;
extendible
force (v: like item)
-- Add v to end.
-- (from SEQUENCE)
require -- from SEQUENCE
extendible: extendible
ensure then -- from SEQUENCE
new_count: count = old count + 1;
item_inserted: has (v)
merge_left (other: like Current)
-- Merge other into current structure before cursor
-- position. Do not move cursor. Empty other.
require
extendible: extendible;
not_off: not before;
other_exists: other /= void
ensure
new_count: count = old count + old other.count;
new_index: index = old index + old other.count;
other_is_empty: other.empty
merge_right (other: like Current)
-- Merge other into current structure after cursor
-- position. Do not move cursor. Empty other.
require
extendible: extendible;
not_off: not after;
other_exists: other /= void
ensure
new_count: count = old count + old other.count;
same_index: index = old index;
other_is_empty: other.empty
put (v: like item)
-- Replace current item by v.
-- (Synonym for replace)
-- (from CHAIN)
require -- from COLLECTION
extendible: extendible
ensure -- from COLLECTION
item_inserted: has (v)
ensure then -- from CHAIN
same_count: count = old count
put_front (v: like item)
-- Add v at beginning.
-- Do not move cursor.
ensure
new_count: count = old count + 1;
item_inserted: first = v
put_i_th (v: like item; i: INTEGER)
-- Put v at i-th position.
-- (from CHAIN)
require -- from TABLE
valid_key: valid_index (k)
ensure then -- from INDEXABLE
insertion_done: i_th (k) = v
put_left (v: like item)
-- Add v to the left of cursor position.
-- Do not move cursor.
require
extendible: extendible;
not_before: not before
ensure
new_count: count = old count + 1;
new_index: index = old index + 1
put_right (v: like item)
-- Add v to the right of cursor position.
-- Do not move cursor.
require
extendible: extendible;
not_after: not after
ensure
new_count: count = old count + 1;
same_index: index = old index
replace (v: G)
-- Replace current item by v.
-- (from ACTIVE)
require -- from ACTIVE
writable: writable
require -- from ACTIVE
writable: writable
ensure -- from ACTIVE
item_replaced: item = v
ensure -- from ACTIVE
item_replaced: item = v
feature -- Removal
prune (v: like item)
-- Remove first occurrence of v, if any,
-- after cursor position.
-- If found, move cursor to right neighbor;
-- if not, make structure exhausted.
require -- from COLLECTION
prunable: prunable
prune_all (v: like item)
-- Remove all occurrences of v.
-- (Reference or object equality,
-- based on object_comparison.)
-- Leave structure exhausted.
require -- from COLLECTION
prunable
ensure -- from COLLECTION
no_more_occurrences: not has (v)
ensure then
is_exhausted: exhausted
remove_left
-- Remove item to the left of cursor position.
-- Do not move cursor.
require
left_exists: index > 1
ensure
new_count: count = old count - 1;
new_index: index = old index - 1
remove_right
-- Remove item to the right of cursor position.
-- Do not move cursor.
require
right_exists: index < count
ensure
new_count: count = old count - 1;
same_index: index = old index
wipe_out
-- Remove all items.
require -- from COLLECTION
prunable
ensure -- from COLLECTION
wiped_out: empty
feature -- Transformation
swap (i: INTEGER)
-- Exchange item at i-th position with item
-- at cursor position.
-- (from CHAIN)
require -- from CHAIN
not_off: not off;
valid_index: valid_index (i)
ensure -- from CHAIN
swapped_to_item: item = old i_th (i);
swapped_from_item: i_th (i) = old item
feature -- Conversion
linear_representation: LINEAR [G]
-- Representation as a linear structure
-- (from LINEAR)
feature -- Duplication
duplicate (n: INTEGER): like Current
-- 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.
require -- from CHAIN
not_off_unless_after: off implies after;
valid_subchain: n >= 0
feature {ANY} -- Inapplicable
remove
-- Remove current item.
-- (from CHAIN)
require -- from ACTIVE
prunable: prunable;
writable: writable
invariant
-- from GENERAL
reflexive_equality: standard_is_equal (Current);
reflexive_conformance: conforms_to (Current);
extendible: extendible;
-- from CHAIN
non_negative_index: index >= 0;
index_small_enough: index <= count + 1;
off_definition: off = ((index = 0) or (index = count + 1));
isfirst_definition: isfirst = ((not empty) and (index = 1));
islast_definition: islast = ((not empty) and (index = count));
item_corresponds_to_index: (not off) implies (item = i_th (index));
-- from ACTIVE
writable_constraint: writable implies readable;
empty_constraint: empty implies (not readable) and (not writable);
-- from BILINEAR
not_both: not (after and before);
empty_property: empty implies (after or before);
before_constraint: before implies off;
-- from LINEAR
after_constraint: after implies off;
-- from TRAVERSABLE
empty_constraint: empty implies off;
-- from FINITE
empty_definition: empty = (count = 0);
non_negative_count: count >= 0;
end -- class DYNAMIC_CHAIN