[fpc-devel] New feature discussion: for-in loop

[Dariusz Mazur]

Paul Ishenin pisze:
> 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;
>
But where is current state of iterator.
next_func need to know  old state and then easy move to next, but were 
state is saved.



second solution  receive old result,  find it in collection, decode past 
state and compute next, but it hurt performance



-- 
  Darek