Class DS_SET_CURSOR PreviousNext

note
description:

    "Cursors for set traversals"

library:    "Gobo Eiffel Structure Library"
author:     "Eric Bezault <ericb@gobosoft.com>"
copyright:  "Copyright (c) 2001, Eric Bezault and others"
license:    "MIT License"
deferred class interface
DS_SET_CURSOR [G]
inherit
DS_LINEAR_CURSOR [G]
    DS_CURSOR [G]
feature -- Access
item: G
        -- Item at cursor position
        -- (From DS_CURSOR.)
    require
        not_off: not off
    deferred
container: DS_SET [G]
        -- Set traversed
        -- (From DS_CURSOR.)
    deferred
feature -- Status report
is_first: BOOLEAN
        -- Is cursor on first item?
        -- (From DS_LINEAR_CURSOR.)
    deferred
    ensure
        not_empty: Result implies not container.is_empty
        not_off: Result implies not off
        definition: Result implies (item = container.first)
after: BOOLEAN
        -- Is there no valid position to right of cursor?
        -- (From DS_LINEAR_CURSOR.)
    deferred
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
    deferred
feature -- Cursor movement
start
        -- Move cursor to first position.
        -- (From DS_LINEAR_CURSOR.)
    deferred
    ensure
        empty_behavior: container.is_empty implies after
        not_empty_behavior: not container.is_empty implies is_first
forth
        -- Move cursor to next position.
        -- (From DS_LINEAR_CURSOR.)
    require
        not_after: not after
    deferred
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
    deferred
go_after
        -- Move cursor to after position.
        -- (From DS_LINEAR_CURSOR.)
    deferred
    ensure
        after: after
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)
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.)
end -- class DS_SET_CURSOR

Copyright 2001, Eric Bezault
mailto:
ericb@gobosoft.com
http:
//www.gobosoft.com
Last Updated: 27 March 2001

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