indexing
description: "Simple linked lists"
author: "Patrick Schoenbach"
class interface
SIMPLE_LIST [G]
create
make
-- Create an empty list.
-- (from LINKED_LIST)
ensure -- from LINKED_LIST
is_before: before
feature -- Initialization
make
-- Create an empty list.
-- (from LINKED_LIST)
ensure -- from LINKED_LIST
is_before: before
feature -- Access
cursor: CURSOR
-- Current cursor position
-- (from LINKED_LIST)
first: like item
-- Item at first position
-- (from LINKED_LIST)
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)
require -- from SEQUENCIAL_CONTAINER
valid_index: valid_index (i)
index: INTEGER
-- Index of current position
-- (from LINKED_LIST)
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
-- Current item
-- (from LINKED_LIST)
require -- from ACTIVE
readable: readable
require -- from TRAVERSABLE
not_off: not off
require -- from SEQUENCIAL_CONTAINER
not_off: not off
last: like item
-- Item at last position
-- (from LINKED_LIST)
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
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
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
capacity: INTEGER
-- Capacity of list
count: INTEGER
-- Number of items
-- (from LINKED_LIST)
feature -- Status report
after: BOOLEAN
-- Is there no valid cursor position to the right of cursor?
-- (from LINKED_LIST)
before: BOOLEAN
-- Is there no valid cursor position to the left of cursor?
-- (from LINKED_LIST)
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.)
-- (from DYNAMIC_CHAIN)
Full: BOOLEAN is false
-- Is structured filled to capacity? (Answer: no.)
-- (from LINKED_LIST)
Insertable: BOOLEAN is true
-- Can items be inserted in the middle of container? (Answer: no)
isfirst: BOOLEAN
-- Is cursor at first position?
-- (from LINKED_LIST)
ensure -- from CHAIN
valid_position: Result implies not empty
islast: BOOLEAN
-- Is cursor at last position?
-- (from LINKED_LIST)
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 LINKED_LIST)
prunable: BOOLEAN
-- May items be removed? (Answer: yes.)
-- (from DYNAMIC_CHAIN)
readable: BOOLEAN
-- Is there a current item that may be read?
-- (from LINKED_LIST)
Resizable: BOOLEAN is false
-- Can container be resized? (Answer: no)
valid_cursor (p: CURSOR): BOOLEAN
-- Can the cursor be moved to position p?
-- (from LINKED_LIST)
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))
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 item.
-- (from LINKED_LIST)
require -- from BILINEAR
not_before: not before
ensure then -- from BILINEAR
moved_back: index = old index - 1
finish
-- Move cursor to last position.
-- (Go before if empty)
-- (from LINKED_LIST)
ensure then -- from CHAIN
at_last: not empty implies islast
ensure then -- from LINKED_LIST
empty_convention: empty implies before
forth
-- Move cursor to next position.
-- (from LINKED_LIST)
require -- LIST
precursor: True
require -- from LINEAR
not_after: not after
require -- from SEQUENCIAL_CONTAINER
not_after: not after
ensure then -- from LIST
moved_forth: index = old index + 1
ensure then -- from LINEAR_CONTAINER
next_position: index = old index + 1
go_i_th (i: INTEGER)
-- Move cursor to i-th position.
-- (from LINKED_LIST)
require -- from CHAIN
valid_cursor_index: valid_cursor_index (i)
require -- from SEQUENCIAL_CONTAINER
valid_index: valid_index (i)
ensure -- from CHAIN
position_expected: index = i
ensure -- from SEQUENCIAL_CONTAINER
i_th_position: index = i
go_to (p: CURSOR)
-- Move cursor to position p.
-- (from LINKED_LIST)
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 offset is too big.
-- (from LINKED_LIST)
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)
ensure then -- from LINKED_LIST
moved_if_inbounds: ((old index + i) >= 0 and (old index + i) <= (count + 1)) implies index = (old index + i);
before_set: (old index + i) <= 0 implies before;
after_set: (old index + i) >= (count + 1) implies after
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.
-- (from LINKED_LIST)
require -- CHAIN
precursor: True
require -- from SEQUENCIAL_CONTAINER
not_empty: not empty
ensure then -- from CHAIN
at_first: not empty implies isfirst
ensure then -- from LINKED_LIST
empty_convention: empty implies after
ensure -- from SEQUENCIAL_CONTAINER
cursor_at_start: isfirst
ensure then -- from LINKED_LIST
empty_convention: empty implies after
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: like item)
-- Add v to end.
-- Do not move cursor.
-- (from LINKED_LIST)
require -- from COLLECTION
extendible: extendible
require -- from SEQUENCIAL_CONTAINER
not_full: not full
ensure -- from COLLECTION
item_inserted: has (v)
ensure then -- from BAG
one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1
ensure then -- from LINEAR_CONTAINER
extended: i_th (count) = v;
count_increased: count = old count + 1;
index_unchanged: not old empty implies index = old index
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.
-- (from LINKED_LIST)
require -- from DYNAMIC_CHAIN
extendible: extendible;
not_off: not before;
other_exists: other /= void
ensure -- from DYNAMIC_CHAIN
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.
-- (from LINKED_LIST)
require -- from DYNAMIC_CHAIN
extendible: extendible;
not_off: not after;
other_exists: other /= void
ensure -- from DYNAMIC_CHAIN
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
require -- from SEQUENCIAL_CONTAINER
not_off: not off
ensure -- from COLLECTION
item_inserted: has (v)
ensure then -- from CHAIN
same_count: count = old count
ensure then -- from LINEAR_CONTAINER
replaced: item = v;
count_unchanged: count = old count;
index_unchanged: index = old index
ensure then -- from CHAIN
same_count: count = old count
put_front (v: like item)
-- Add v to beginning.
-- Do not move cursor.
-- (from LINKED_LIST)
ensure -- from DYNAMIC_CHAIN
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.
-- (from LINKED_LIST)
require -- from DYNAMIC_CHAIN
extendible: extendible;
not_before: not before
require -- from SEQUENCIAL_CONTAINER
insertable: insertable;
not_full: not full;
not_before: not before
ensure -- from DYNAMIC_CHAIN
new_count: count = old count + 1;
new_index: index = old index + 1
ensure then -- from LINEAR_CONTAINER
inserted: i_th (index - 1) = v;
count_increased: count = old count + 1;
index_increased: index = old index + 1
put_right (v: like item)
-- Add v to the right of cursor position.
-- Do not move cursor.
-- (from LINKED_LIST)
require -- from DYNAMIC_CHAIN
extendible: extendible;
not_after: not after
require -- from SEQUENCIAL_CONTAINER
insertable: insertable;
not_full: not full;
not_after: not after
ensure -- from DYNAMIC_CHAIN
new_count: count = old count + 1;
same_index: index = old index
ensure then -- from LINEAR_CONTAINER
inserted: i_th (index + 1) = v;
count_increased: count = old count + 1;
index_unchanged: index = old index
replace (v: like item)
-- Replace current item by v.
-- (from LINKED_LIST)
require -- from ACTIVE
writable: writable
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.
-- (from DYNAMIC_CHAIN)
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.
-- (from DYNAMIC_CHAIN)
require -- DYNAMIC_CHAIN
precursor: True
require -- from COLLECTION
prunable
ensure then -- from DYNAMIC_CHAIN
is_exhausted: exhausted
ensure -- from COLLECTION
no_more_occurrences: not has (v)
ensure then -- from DYNAMIC_CHAIN
is_exhausted: exhausted
remove
-- Remove current item.
-- Move cursor to right neighbor
-- (or after if no right neighbor).
-- (from LINKED_LIST)
require -- from ACTIVE
prunable: prunable;
writable: writable
require -- from SEQUENCIAL_CONTAINER
prunable: prunable;
not_empty: not empty;
not_off: not off
ensure then -- from DYNAMIC_LIST
after_when_empty: empty implies after
ensure then -- from LINEAR_CONTAINER
count_decreased: count = old count - 1;
index_unchanged: not off implies index = old index
remove_left
-- Remove item to the left of cursor position.
-- Do not move cursor.
-- (from LINKED_LIST)
require -- from DYNAMIC_CHAIN
left_exists: index > 1
require else -- from DYNAMIC_LIST
not_before: not before
ensure -- from DYNAMIC_CHAIN
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.
-- (from LINKED_LIST)
require -- from DYNAMIC_CHAIN
right_exists: index < count
ensure -- from DYNAMIC_CHAIN
new_count: count = old count - 1;
same_index: index = old index
wipe_out
-- Remove all items.
-- (from LINKED_LIST)
require -- from COLLECTION
prunable
ensure -- from COLLECTION
wiped_out: empty
ensure then -- from DYNAMIC_LIST
is_before: before
ensure -- from SEQUENCIAL_CONTAINER
empty: empty
feature -- Resizing
resize (n: INTEGER)
-- Resize container to n elements.
require -- from SEQUENCIAL_CONTAINER
resizable: resizable;
size_increasing: n > capacity
ensure -- from SEQUENCIAL_CONTAINER
resized: capacity = n
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.
-- (from DYNAMIC_CHAIN)
require -- from CHAIN
not_off_unless_after: off implies after;
valid_subchain: n >= 0
invariant
-- from GENERAL
reflexive_equality: standard_is_equal (Current);
reflexive_conformance: conforms_to (Current);
-- from LINEAR_CONTAINER
after_definition: after = (index = count + 1);
before_definition: before = (index = 0);
isfirst_definition: isfirst = (not empty and then (index = 1));
islast_definition: islast = (not empty and then (index = count));
-- from SEQUENCIAL_CONTAINER
empty_definition: empty = (count = 0);
off_definition: off = (before or after);
empty_constraint: empty implies off;
count_range: 0 <= count and count <= capacity;
-- from LINKED_LIST
prunable: prunable;
-- from LIST
before_definition: before = (index = 0);
after_definition: after = (index = count + 1);
-- 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;
-- from DYNAMIC_CHAIN
extendible: extendible;
end -- class SIMPLE_LIST