[[Property:modification_date|Wed, 17 Apr 2019 14:09:18 GMT]]
[[Property:publication_date|Thu, 06 Sep 2018 15:17:57 GMT]]
[[Property:uuid|96077603-DD2D-4D8C-A486-AF4BD066613A]]
[[Property:weight|2000]]
[[Property:title|Iterating on a LIST]]
There are three Eiffel mechanisms to iterate on every element of a `LIST`.

=== the `across` loop ===
The `across` can be used on every `ITERABLE` object (including `LIST` objects).

<code>
	print_elements (a_list: LIST[INTEGER])
			-- Print every elements on `a_list`
		do
			across a_list as ic loop
				print (ic.item.out + "%N")
			end
		end
</code>

Note that the temporary variable (`ic` in the example) represents an iterator of the `ITERABLE` object, and not directly an element like in many other languages (like the `for` structure in Python for example).

=== the `from until` loop syntax===
This syntax offer more possibilities than the `across` loop, but is riskier.

<code>
	print_elements (a_list:LIST[INTEGER])
			-- Print every elements on `a_list`
		do
			from
				a_list.start
			until
				a_list.exhausted
			loop
				print (a_list.item.out + "%N")
				a_list.forth
			end
		end
</code>

=== Using Eiffel agents and `{LIST}.do_all, ....` ===
It is possible to use agents in conjunction with the `LIST` features `do_all`, `do_if`, `there_exists`, and `for_all` which are inherited from the class `LINEAR`.
<code>
	list_traversal_agents
			-- Example of traversing a list with do_all
		local
			a_list: LINKED_LIST [STRING]
		do
				-- Insert some elements in a_list
			create a_list.make
			a_list.extend ("The Moon Is Full")
			a_list.extend ("Master charge")
			a_list.extend ("Black cat bone")
			a_list.do_all (agent {STRING}.append (" - Albert Collins"))
			a_list.do_all (agent print_element)
		end

	print_element (a_element: STRING)
			-- Print `a_element` to standard output
		do
			io.put_string (a_element)
			io.put_new_line
		end
</code>