Paul Ishenin пишет:
Marc Weustink wrote:
I can see a use for using iterators in a for loop, however they should
be declared with some keyword.
Something like
type
TListIterator = iterator(TList, init_func, next_func, check_func)
function init_func: Boolean;
function next_func: <element type>
function check_func: Boolean;
end;
begin
for element in list using TListIterator do...
IMO this is more pascal than using some interface or predefined
function names.
Good idea. What is iterator internally? Is this an object with the
special header?
Is it internall the same as:
TListIterator = object
function init_func(AList: TList): Boolean;
function next_func: Pointer;
function check_func: Boolean;
end;
Don't comlicate it more than necessary:
1) An object (or record with methods, provided you implement it first
:-) is preferable over class, since using it can help avoiding
construction/destruction, memory allocations, and implicit try..finally.
2) Using objects/records also enables you to use operators to encode the
iterator. This isn't possible for classes.
3) next_func and check_func above can be coalesced to a single
function next(out obj: TItem): Boolean;
4) The syntax 'for element in list using TListIterator' is kind of
redundant. I'd suggest:
for element in list.GetForwardIterator do ..., or even
for element in list.GetSubItems(arguments) do ...
Regards,
Sergei
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