Class DS_DYNAMIC_CURSOR PreviousNext

note
description:

    "Cursors for dynamically modifiable data structure traversals"

library:    "Gobo Eiffel Structure Library"
author:     "Eric Bezault <ericb@gobosoft.com>"
copyright:  "Copyright (c) 1999, Eric Bezault and others"
license:    "MIT License"
deferred class interface
DS_DYNAMIC_CURSOR [G]
inherit
DS_CURSOR [G]
feature -- Access
item: G
        -- Item at cursor position
        -- (From DS_CURSOR.)
    require
        not_off: not off
    deferred
container: DS_TRAVERSABLE [G]
        -- Data structure traversed
        -- (From DS_CURSOR.)
    deferred
feature -- Status report
off: BOOLEAN
        -- Is there no item at cursor position?
        -- (From DS_CURSOR.)
    deferred
same_position (other: like Current): BOOLEAN
        -- Is current cursor at same position as other?
        -- (From DS_CURSOR.)
    require
        other_not_void: other /= Void
    deferred
feature -- Cursor movement
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)
    deferred
    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.
    require
        not_off: not off
    deferred
    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.
    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.)
end -- class DS_DYNAMIC_CURSOR

Copyright 1999, Eric Bezault
mailto:
ericb@gobosoft.com
http:
//www.gobosoft.com
Last Updated: 31 July 1999

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