Class DS_CURSOR

Class DS_CURSOR

note

description:

    "Cursors for 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_CURSOR [G]

feature -- Access

item: G
        -- Item at cursor position
    require
        not_off: not off
    deferred

container: DS_TRAVERSABLE [G]
        -- Data structure traversed
    deferred

feature -- Status report

off: BOOLEAN
        -- Is there no item at cursor position?
    deferred

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

feature -- Cursor movement

go_to (other: like Current)
        -- Move cursor to other's position.
    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

end -- class DS_CURSOR