Class DS_HASH_TABLE

Class DS_HASH_TABLE_CURSOR

note

description:

    "Cursors for hash table traversals"

library:    "Gobo Eiffel Structure Library"
author:     "Eric Bezault <ericb@gobosoft.com>"
copyright:  "Copyright (c) 1999, Eric Bezault and others"
license:    "MIT License"

class interface

DS_HASH_TABLE_CURSOR [G, K -> HASHABLE]

inherit

DS_SPARSE_TABLE_CURSOR [G, K]
    DS_BILINEAR_CURSOR [G]
        DS_LINEAR_CURSOR [G]
            DS_CURSOR [G]
    DS_DYNAMIC_CURSOR [G]
        DS_CURSOR [G]

create

make (a_table: like container)
        -- Create a new cursor for a_table.
        -- (From DS_SPARSE_TABLE_CURSOR.)
    require
        a_table_not_void: a_table /= Void
    ensure
        container_set: container = a_table
        before: before

feature -- Access

item: G
        -- Item at cursor position
        -- (From DS_CURSOR.)
    require
        not_off: not off

key: K
        -- Key at cursor position
        -- (From DS_SPARSE_TABLE_CURSOR.)
    require
        not_off: not off

container: DS_HASH_TABLE [G, K]
        -- Hash table traversed
        -- (From DS_CURSOR.)

feature -- Status report

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

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

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

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

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

same_position (other: like Current): BOOLEAN
        -- Is current cursor at same position as other?
        -- (From DS_CURSOR.)
    require
        other_not_void: other /= Void

feature -- Cursor movement

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

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

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

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

search_forth (v: G)
        -- Move to first position at or after current
        -- position where item and v are equal.
        -- (Use equality_tester's criterion from container
        -- if not void, use `=' criterion otherwise.)
        -- Move after if not found.
        -- (From DS_LINEAR_CURSOR.)
    require
        not_off: not off or after

search_back (v: G)
        -- Move to first position at or before current
        -- position where item and v are equal.
        -- (Use equality_tester's criterion from container
        -- if not void, use `=' criterion otherwise.)
        -- Move before if not found.
        -- (From DS_BILINEAR_CURSOR.)
    require
        not_off: not off or before

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

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

go_to (other: like Current)
        -- Move cursor to other's position.
        -- (From DS_CURSOR.)
    require
        other_not_void: other /= Void
        valid_cursor: container.valid_cursor (other)
    ensure
        same_position: same_position (other)

feature -- Comparison

is_equal (other: like Current): BOOLEAN
        -- Are other and current cursor at the same position?
        -- (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)

feature -- Duplication

copy (other: like Current)
        -- Copy other to current cursor.
        -- (From GENERAL.)
    require
        other_not_void: other /= Void
        type_identity: same_type (other)
    ensure
        is_equal: is_equal (other)

feature -- Element change

replace (v: G)
        -- Replace item at cursor position by v.
        -- (From DS_DYNAMIC_CURSOR.)
    require
        not_off: not off
    ensure
        replaced: item = v

swap (other: DS_DYNAMIC_CURSOR [G])
        -- Exchange items at current and other's positions.
        -- Note: cursors may reference two different containers.
        -- (From DS_DYNAMIC_CURSOR.)
    require
        not_off: not off
        other_not_void: other /= Void
        other_not_off: not other.off
    ensure
        new_item: item = old (other.item)
        new_other: other.item = old item

invariant

container_not_void: container /= Void
empty_constraint: container.is_empty implies off
    -- (From DS_CURSOR.)

after_constraint: after implies off
    -- (From DS_LINEAR_CURSOR.)

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

end -- class DS_HASH_TABLE_CURSOR