Class DS_MULTIARRAYED_SPARSE_TABLE |

    indexing

>     description:

>         "Sparse tables implemented with multi-arrays. Ancestor of %
>         %hash tables which should supply its hashing mechanism."

>     library:    "Gobo Eiffel Structure Library"
>     author:     "Eric Bezault <ericb@gobosoft.com>"
>     copyright:  "Copyright (c) 2001, Eric Bezault and others"
>     license:    "Eiffel Forum License v2 (see forum.txt)"

    deferred class interface

>     DS_MULTIARRAYED_SPARSE_TABLE [G, K]

    inherit

>     DS_SPARSE_TABLE [G, K]
>         DS_TABLE [G, K]
>             DS_CONTAINER [G]
>         DS_BILINEAR [G]
>             DS_LINEAR [G]
>                 DS_TRAVERSABLE [G]
>                     DS_CONTAINER [G]
>                 DS_SEARCHABLE [G]
>                     DS_CONTAINER [G]
>         DS_RESIZABLE [G]
>             DS_CONTAINER [G]

    feature {NONE} -- Initialization

>     make_default
>             -- Create an empty container and allocate memory
>             -- space for at least default_capacity items. Array
>             -- chunks will have a size of default_chunk_size.
>             -- Use `=' as comparison criterion for items.
>             -- Use equal as comparison criterion for keys.
>             -- (From DS_CONTAINER.)
>         ensure
>             empty: is_empty
>             capacity_set: capacity = default_capacity
>             chunk_size_set: chunk_size = default_chunk_size
>             before: before

    feature -- Access

>     infix "@", item (k: K): G
>             -- Item associated with k
>             -- (From DS_TABLE.)
>         require
>             valid_entry: has (k)

>     key (k: K): K
>             -- Key associated with k
>             -- (From DS_SPARSE_TABLE.)
>         require
>             has_k: has (k)

>     found_item: G
>             -- Item found by last call to search
>             -- (From DS_SPARSE_TABLE.)
>         require
>             item_found: found

>     found_key: K
>             -- Key of item found by last call to search
>             -- (From DS_SPARSE_TABLE.)
>         require
>             key_found: found

>     item_for_iteration: G
>             -- Item at internal cursor position
>             -- (From DS_TRAVERSABLE.)
>         require
>             not_off: not off

>     key_for_iteration: K
>             -- Key at internal cursor position
>             -- (From DS_SPARSE_TABLE.)
>         require
>             not_off: not off

>     first: G
>             -- First item in table
>             -- (From DS_LINEAR.)
>         require
>             not_empty: not is_empty
>         ensure
>             has_first: has_item (Result)

>     last: G
>             -- Last item in table
>             -- (From DS_BILINEAR.)
>         require
>             not_empty: not is_empty
>         ensure
>             has_last: has_item (Result)

>     new_cursor: DS_MULTIARRAYED_SPARSE_TABLE_CURSOR [G, K]
>             -- New external cursor for traversal
>             -- (From DS_TRAVERSABLE.)
>         ensure
>             cursor_not_void: Result /= Void
>             valid_cursor: valid_cursor (Result)

>     equality_tester: DS_EQUALITY_TESTER [G]
>             -- Equality tester;
>             -- A void equality tester means that `='
>             -- will be used as comparison criterion.
>             -- (From DS_SEARCHABLE.)

>     key_equality_tester: DS_EQUALITY_TESTER [K]
>             -- Equality tester for keys;
>             -- A void equality tester means that `='
>             -- will be used as comparison criterion.
>             -- (From DS_SPARSE_TABLE.)

    feature -- Measurement

>     count: INTEGER
>             -- Number of items in table
>             -- (From DS_CONTAINER.)

>     capacity: INTEGER
>             -- Maximum number of items in table
>             -- (From DS_RESIZABLE.)

>     default_capacity: INTEGER
>             -- Initial capacity in make_default
>             -- (Default value: 10)
>             -- (From DS_RESIZABLE.)
>         ensure
>             default_capacity_positive: Result >= 0

>     chunk_size: INTEGER
>             -- Size of array chunks

>     default_chunk_size: INTEGER
>             -- Default value for chunk_size
>             -- (Default value: 30000)
>         ensure
>             default_chunk_size_positive: Result > 0

>     occurrences (v: G): INTEGER
>             -- Number of times v appears in table
>             -- (Use equality_tester's comparison criterion
>             -- if not void, use `=' criterion otherwise.)
>             -- (From DS_SEARCHABLE.)
>         ensure
>             positive: Result >= 0
>             has: has_item (v) implies Result >= 1

    feature -- Status report

>     has (k: K): BOOLEAN
>             -- Is there an item associated with k?
>             -- (From in DS_TABLE.)
>         ensure
>             valid_key: Result implies valid_key (k)

>     has_item (v: G): BOOLEAN
>             -- Does table include v?
>             -- (Use equality_tester's comparison criterion
>             -- if not void, use `=' criterion otherwise.)
>             -- (From has in DS_SEARCHABLE.)
>         ensure
>             not_empty: Result implies not is_empty

>     found: BOOLEAN
>             -- Did last call to search succeed?
>             -- (From DS_SPARSE_TABLE.)

>     is_empty: BOOLEAN
>             -- Is table empty?
>             -- (From DS_CONTAINER.)

>     is_full: BOOLEAN
>             -- Is table full?
>             -- (From DS_RESIZABLE.)

>     is_first: BOOLEAN
>             -- Is internal cursor on first item?
>             -- (From DS_LINEAR.)
>         ensure
>             not_empty: Result implies not is_empty
>             not_off: Result implies not off
>             definition: Result implies (item_for_iteration = first)

>     is_last: BOOLEAN
>             -- Is internal cursor on last item?
>             -- (From DS_BILINEAR.)
>         ensure
>             not_empty: Result implies not is_empty
>             not_off: Result implies not off
>             definition: Result implies (item_for_iteration = last)

>     after: BOOLEAN
>             -- Is there no valid position to right of internal cursor?
>             -- (From DS_LINEAR.)

>     before: BOOLEAN
>             -- Is there no valid position to left of internal cursor?
>             -- (From DS_BILINEAR.)

>     off: BOOLEAN
>             -- Is there no item at internal cursor position?
>             -- (From DS_TRAVERSABLE.)

>     same_position (a_cursor: like new_cursor): BOOLEAN
>             -- Is internal cursor at same position as a_cursor?
>             -- (From DS_TRAVERSABLE.)
>         require
>             a_cursor_not_void: a_cursor /= Void

>     valid_cursor (a_cursor: DS_CURSOR [G]): BOOLEAN
>             -- Is a_cursor a valid cursor?
>             -- (From DS_TRAVERSABLE.)
>         require
>             a_cursor_not_void: a_cursor /= Void

>     valid_key (k: K): BOOLEAN
>             -- Is k a valid key?
>             -- (From DS_TABLE.)
>         ensure
>             defintion: Result = True

>     same_items (v, u: G): BOOLEAN
>             -- Are v and u considered equal?
>             -- (Use equality_tester's comparison criterion
>             -- if not void, use `=' criterion otherwise.)
>             -- (From DS_SEARCHABLE.)

>     same_equality_tester (other: DS_SEARCHABLE [G]): BOOLEAN
>             -- Does container use the same comparison
>             -- criterion as other?
>             -- (From DS_SEARCHABLE.)
>         require
>             other_not_void: other /= Void

>     equality_tester_settable (a_tester: like equality_tester): BOOLEAN
>             -- Can set_equality_tester be called with a_tester
>             -- as argument in current state of container?
>             -- (Default answer: True.)
>             -- (From DS_SEARCHABLE.)

    feature -- Search

>     search (k: K)
>             -- Search for item at key k.
>             -- If found, set found to true, and set
>             -- found_item to item associated with k.
>             -- (From DS_SPARSE_TABLE.)
>         ensure
>             found_set: found = has (k)
>             found_item_set: found implies (found_item = item (k))

    feature -- Comparison

>     is_equal (other: like Current): BOOLEAN
>             -- Is current table equal to other?
>             -- Do not take cursor positions, capacity
>             -- nor equality_tester into account.
>             -- (From GENERAL.)
>         require
>             other_not_void: other /= Void
>         ensure
>             consistent: standard_is_equal (other) implies Result
>             same_type: Result implies same_type (other)
>             symmetric: Result implies other.is_equal (Current)
>             same_count: Result implies count = other.count

    feature -- Duplication

>     copy (other: like Current)
>             -- Copy other to current table.
>             -- Move all cursors off (unless other = Current).
>             -- (From GENERAL.)
>         require
>             other_not_void: other /= Void
>             type_identity: same_type (other)
>         ensure
>             is_equal: is_equal (other)

    feature -- Setting

>     set_equality_tester (a_tester: like equality_tester)
>             -- Set equality_tester to a_tester.
>             -- A void equality tester means that `='
>             -- will be used as comparison criterion.
>             -- (From DS_SEARCHABLE.)
>         require
>             equality_tester_settable: equality_tester_settable (a_tester)
>         ensure
>             equality_tester_set: equality_tester = a_tester

    feature -- Cursor movement

>     start
>             -- Move internal cursor to first position.
>             -- (From DS_LINEAR.)
>         ensure
>             empty_behavior: is_empty implies after
>             not_empty_behavior: not is_empty implies is_first

>     finish
>             -- Move internal cursor to last position.
>             -- (From DS_BILINEAR.)
>         ensure
>             empty_behavior: is_empty implies before
>             not_empty_behavior: not is_empty implies is_last

>     forth
>             -- Move internal cursor to next position.
>             -- (From DS_LINEAR.)
>         require
>             not_after: not after

>     back
>             -- Move internal cursor to previous position.
>             -- (From DS_BILINEAR.)
>         require
>             not_before: not before

>     search_forth (v: G)
>             -- Move internal cursor to first position at or after current
>             -- position where item_for_iteration and v are equal.
>             -- (Use equality_tester's comparison criterion
>             -- if not void, use `=' criterion otherwise.)
>             -- Move after if not found.
>             -- (From DS_LINEAR.)
>         require
>             not_off: not off or after

>     search_back (v: G)
>             -- Move internal cursor to first position at or before current
>             -- position where item_for_iteration and v are equal.
>             -- (Use equality_tester's comparison criterion
>             -- if not void, use `=' criterion otherwise.)
>             -- Move before if not found.
>             -- (From DS_BILINEAR.)
>         require
>             not_off: not off or before

>     go_after
>             -- Move cursor to after position.
>             -- (From DS_LINEAR.)
>         ensure
>             after: after

>     go_before
>             -- Move cursor to before position.
>             -- (From DS_BILINEAR.)
>         ensure
>             before: before

>     go_to (a_cursor: like new_cursor)
>             -- Move internal cursor to a_cursor's position.
>             -- (From DS_TRAVERSABLE.)
>         require
>             cursor_not_void: a_cursor /= Void
>             valid_cursor: valid_cursor (a_cursor)
>         ensure
>             same_position: same_position (a_cursor)

    feature -- Element change

>     replace (v: G; k: K)
>             -- Replace item associated with k by v.
>             -- Do not move cursors.
>             -- (From DS_TABLE.)
>         require
>             valid_entry: has (k)
>         ensure
>             replaced: item (k) = v
>             same_count: count = old count

>     replace_found_item (v: G)
>             -- Replace item associated with
>             -- the key of found_item by v.
>             -- Do not move cursors.
>             -- (From DS_SPARSE_TABLE.)
>         require
>             item_found: found
>         ensure
>             replaced: found_item = v
>             same_count: count = old count

>     put (v: G; k: K)
>             -- Associate v with key k.
>             -- Do not move cursors.
>             -- (From DS_SPARSE_TABLE.)
>         require
>             not_full: not is_full
>             valid_key: valid_key (k)
>         ensure
>             inserted: has (k) and then item (k) = v
>             same_count: (old has (k)) implies (count = old count)
>             one_more: (not old has (k)) implies (count = old count + 1)

>     put_new (v: G; k: K)
>             -- Associate v with key k.
>             -- Do not move cursors.
>             -- (From DS_SPARSE_TABLE.)
>         require
>             not_full: not is_full
>             valid_key: valid_key (k)
>             new_item: not has (k)
>         ensure
>             one_more: count = old count + 1
>             inserted: has (k) and then item (k) = v

>     force (v: G; k: K)
>             -- Associate v with key k.
>             -- Resize table if necessary.
>             -- Do not move cursors.
>             -- (From put in DS_TABLE.)
>         require
>             valid_key: valid_key (k)
>         ensure
>             inserted: has (k) and then item (k) = v
>             same_count: (old has (k)) implies (count = old count)
>             one_more: (not old has (k)) implies (count = old count + 1)

>     force_new (v: G; k: K)
>             -- Associate v with key k.
>             -- Resize table if necessary.
>             -- Do not move cursors.
>             -- (From put_new in DS_TABLE.)
>         require
>             valid_key: valid_key (k)
>             new_item: not has (k)
>         ensure
>             one_more: count = old count + 1
>             inserted: has (k) and then item (k) = v

>     force_last (v: G; k: K)
>             -- Associate v with key k. Put v at the end of table
>             -- if no item was already associated with k, or replace
>             -- existing item otherwise.
>             -- Resize table if necessary.
>             -- Do not move cursors.
>             -- (From DS_SPARSE_TABLE.)
>         ensure
>             same_count: (old has (k)) implies (count = old count)
>             one_more: (not old has (k)) implies (count = old count + 1)
>             inserted: has (k) and then item (k) = v
>             last: (not old has (k)) implies last = v

>     swap (k, l: K)
>             -- Exchange items associated with k and l.
>             -- (From DS_TABLE.)
>         require
>             valid_k: has (k)
>             valid_l: has (l)
>         ensure
>             same_count: count = old count
>             new_k: item (k) = old item (l)
>             new_l: item (l) = old item (k)

    feature -- Removal

>     remove (k: K)
>             -- Remove item associated with k.
>             -- Move any cursors at this position forth.
>             -- (From DS_TABLE.)
>         require
>             valid_key: valid_key (k)
>         ensure
>             same_count: (not old has (k)) implies (count = old count)
>             one_less: (old has (k)) implies (count = old count - 1)
>             removed: not has (k)

>     remove_found_item
>             -- Remove item found by last call to search.
>             -- Move any cursors at this position forth.
>             -- (From DS_SPARSE_TABLE.)
>         require
>             item_found: found
>         ensure
>             one_less: count = old count - 1

>     wipe_out
>             -- Remove all items from table.
>             -- Move all cursors off.
>             -- (From DS_CONTAINER.)
>         ensure
>             wiped_out: is_empty

    feature -- Resizing

>     resize (n: INTEGER)
>             -- Resize table so that it can contain
>             -- at least n items. Do not lose any item.
>             -- Move all cursors off.
>             -- (From DS_RESIZABLE.)
>         require
>             n_large_enough: n >= capacity
>         ensure
>             capacity_set: capacity = n

    invariant

>     positive_count: count >= 0
>     empty_definition: is_empty = (count = 0)
>         -- (From DS_CONTAINER.)

>     empty_constraint: is_empty implies off
>         -- (From DS_TRAVERSABLE.)

>     after_constraint: after implies off
>         -- (From DS_LINEAR.)

>     not_both: not (after and before)
>     before_constraint: before implies off
>         -- (From DS_BILINEAR.)

>     count_constraint: count <= capacity
>     full_definition: is_full = (count = capacity)
>         -- (From DS_RESIZABLE.)

>     chunk_size_positive: chunk_size > 0

    end -- class DS_MULTIARRAYED_SPARSE_TABLE