note description: "Objects that are able to iterate over linear structures" library: "Free implementation of ELKS library" legal: "See notice at end of class." status: "See notice at end of class." names: iterators, iteration, linear_iterators, linear_iteration; date: "$Date$" revision: "$Revision$" class LINEAR_ITERATOR [G] inherit ITERATOR [G] redefine target, set end create set feature -- Initialization set (s: like target) -- Make `s' the new target of iterations. do target := s end feature -- Access item: G -- The item at cursor position in `target' require not_off: not target.off do Result := target.item end item_tuple: TUPLE [G] -- Tuple containing a single element, -- the item at cursor position in `target''' require not_off: not target.off do Result := [target.item] ensure item_tuple_attached: Result /= Void end target: LINEAR [G] -- The structure to which iteration features will apply. feature -- Cursor movement start -- Move to first position of `target'. do target.start end forth -- Move to next position of `target'. do target.forth end off: BOOLEAN -- Is position of `target' off? do Result := target.off end exhausted: BOOLEAN -- Is `target' exhausted? do Result := target.exhausted end feature -- Iteration do_while (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- and including first one not satisfying `test'. -- (from the `start' of `target') do start continue_while (action, test) ensure then finished: not exhausted implies not test.item ([target.item]) end continue_while (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- and including first one not satisfying `test' -- (from the current position of `target'). require else invariant_satisfied: invariant_value do from if not exhausted then action.call ([target.item]) end invariant invariant_value until exhausted or else not test.item ([target.item]) loop forth if not exhausted then action.call ([target.item]) end end ensure then finished: not exhausted implies not test.item ([target.item]) end while_do (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- but excluding first one not satisfying `test'. -- (Apply to full list if all items satisfy `test'.) do start while_continue (action, test) ensure then finished: not exhausted implies not test.item ([target.item]) end while_continue (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- but excluding first one not satisfying `test'. do from invariant invariant_value until exhausted or else not test.item ([target.item]) loop action.call ([target.item]) forth end ensure finished: not exhausted implies not test.item ([target.item]) end until_do (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- but excluding first one satisfying `test'. -- (Apply to full list if no item satisfies `test'.) do start until_continue (action, test) ensure then achieved: not exhausted implies test.item ([target.item]) end until_continue (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' from current -- position, up to but excluding first one satisfying `test'. require invariant_satisfied: invariant_value do from invariant invariant_value until exhausted or else test.item ([target.item]) loop action.call ([item]) forth end ensure achieved: exhausted or else test.item ([target.item]) invariant_satisfied: invariant_value end do_until (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- and including first one satisfying `test'. do start continue_until (action, test) ensure then achieved: not exhausted implies test.item ([target.item]) end continue_until (action: PROCEDURE [G]; test: FUNCTION [G, BOOLEAN]) -- Apply `action' to every item of `target' up to -- and including first one satisfying `test'. -- (from the current position of `target'). require invariant_satisfied: invariant_value do from if not exhausted then action.call ([target.item]) end invariant invariant_value until exhausted or else test.item ([target.item]) loop forth if not exhausted then action.call ([target.item]) end end ensure then achieved: not exhausted implies test.item ([target.item]) end search (test: FUNCTION [G, BOOLEAN]; b: BOOLEAN) -- Search the first item of `target' for which `test' -- has the same value as `b' (both true or both false). do start continue_search (test, b) end continue_search (test: FUNCTION [G, BOOLEAN]; b: BOOLEAN) -- Search the first item of `target' -- satisfying: `test' equals to `b' -- (from the current position of `target'). do from invariant invariant_value until exhausted or else (b = test.item ([target.item])) loop forth end ensure then found: not exhausted = (b = test.item ([target.item])) end do_for (action: PROCEDURE [G]; i, n, k: INTEGER) -- Apply `action' to every `k'-th item, -- `n' times if possible, starting from `i'-th. require valid_start: i >= 1 valid_repetition: n >= 0 valid_skip: k >= 1 local j: INTEGER do from start j := 1 invariant j >= 1 and j <= i until exhausted or else j = i loop forth j := j + 1 variant i - j end continue_for (action, n, k) end continue_for (action: PROCEDURE [G]; n, k: INTEGER) -- Apply `action' to every `k'-th item, -- `n' times if possible. require valid_repetition: n >= 0 valid_skip: k >= 1 local i, j: INTEGER do from invariant i >= 0 and i <= n until exhausted or else i = n loop action.call ([target.item]) i := i + 1 from j := 0 invariant j >= 0 and j <= k until exhausted or else j = k loop forth j := j + 1 variant k - j end variant n - i end end for_all (test: FUNCTION [G, BOOLEAN]): BOOLEAN -- Does `test' return true for -- all items of `target'? do search (test, False) Result := exhausted end there_exists (test: FUNCTION [G, BOOLEAN]): BOOLEAN -- Does `test' return true for -- at least one item of `target'? do search (test, True) Result := not exhausted end invariant target_exists: target /= Void note copyright: "Copyright (c) 1984-2012, Eiffel Software and others" license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)" source: "[ Eiffel Software 5949 Hollister Ave., Goleta, CA 93117 USA Telephone 805-685-1006, Fax 805-685-6869 Website http://www.eiffel.com Customer support http://support.eiffel.com ]" end