indexing
description: "Structures that can be traversed forward and backward"
library: "Gobo Eiffel Structure Library"
author: "Eric Bezault <ericb@gobo.demon.co.uk>"
copyright: "Copyright (c) 1997, Eric Bezault"
deferred class interface
DS_BILINEAR [G]
feature -- Access
first: G
-- First item in structure
-- (from DS_LINEAR)
require -- from DS_LINEAR
not_empty: not is_empty
ensure -- from DS_LINEAR
has_first: has (Result)
last: G
-- Last item in structure
require
not_empty: not is_empty
ensure
has_last: has (Result)
new_cursor: DS_BILINEAR_CURSOR [G]
-- New cursor for traversal
ensure -- from DS_TRAVERSABLE
cursor_not_void: Result /= void;
valid_cursor: valid_cursor (Result)
searcher: DS_BILINEAR_SEARCHER [G]
-- Structure searcher
feature -- Measurement
count: INTEGER
-- Number of items in structure
-- (from DS_CONTAINER)
occurrences (v: G): INTEGER
-- Number of times v appears in structure
-- (Use searcher's comparison criterion.)
-- (from DS_SEARCHABLE)
ensure -- from DS_SEARCHABLE
positive: Result >= 0;
has: has (v) implies Result >= 1
feature -- Comparison
is_equal (other: like Current): BOOLEAN
-- Is current structure equal to other?
-- (from DS_CONTAINER)
require -- from GENERAL
other_not_void: other /= void
ensure -- from GENERAL
symmetric: Result implies other.is_equal (Current);
consistent: standard_is_equal (other) implies Result
ensure then -- from DS_CONTAINER
same_count: Result implies count = other.count
ensure then -- from DS_CONTAINER
same_count: Result implies count = other.count
feature -- Status report
has (v: G): BOOLEAN
-- Does structure incluse v?
-- (Use searcher's comparison criterion.)
-- (from DS_SEARCHABLE)
ensure -- from DS_SEARCHABLE
not_empty: Result implies not is_empty
is_empty: BOOLEAN
-- Is structure empty?
-- (from DS_CONTAINER)
valid_cursor (a_cursor: like new_cursor): BOOLEAN
-- Is a_cursor a valid cursor?
-- (A cursor might become invalid if structure
-- has been modified during traversal.)
-- (from DS_TRAVERSABLE)
require -- from DS_TRAVERSABLE
a_cursor_not_void: a_cursor /= void
ensure -- from DS_TRAVERSABLE
is_valid: Result implies a_cursor.is_valid
feature -- Removal
wipe_out
-- Remove all items from structure.
-- (from DS_CONTAINER)
ensure -- from DS_CONTAINER
wipe_out: is_empty
ensure -- from DS_CONTAINER
wipe_out: is_empty
feature -- Setting
set_searcher (a_searcher: like searcher)
-- Set searcher to a_searcher.
-- (from DS_SEARCHABLE)
require -- from DS_SEARCHABLE
a_searcher_not_void: a_searcher /= void
ensure -- from DS_SEARCHABLE
searcher_set: searcher = a_searcher
invariant
-- from GENERAL
reflexive_equality: standard_is_equal (Current);
reflexive_conformance: conforms_to (Current);
-- from DS_CONTAINER
positive_count: count >= 0;
empty_definition: is_empty = (count = 0);
-- from DS_SEARCHABLE
searcher_not_void: searcher /= void;
end -- class DS_BILINEAR