Dariusz Mazur wrote:
Can You give example of this:
where
for i in List using GetEnumerator
is better than
for i in List.GetEnumerator
Of course. for-in loop expect to have a collection not an enumerator.
What enumerator should for-in loop to choose in the next case:
[example]
TMyListEnumerator = class
public
function GetEnumerator: TMyListEnumeratorEnumerator;
function MoveNext: Boolean;
property Current: something;
end;
TMyList = class
public
function GetEnumerator: TMyListEnumerator;
function GetAnotherEnumerator: TMyListAnotherEnumerator;
end;
var
List: TMyList;
begin
for i in List.GetEnumerator do
end;
[/example]
Loop will choose TMyListEnumeratorEnumerator, but is it desired?
'using' keyword solves this ambiguity very easy:
for CollectionElement in Collection using CollectionEnumerator do
And second: You cant pass enumerator as param.
Maybe you understood me wrong? I proposed the 'using' keyword as an
extension to the current implementation. It would not be required. If
not used then it will work as now but if used then compiler will
search for the given identifier and use it instead of
operator/GetEnumerator method.
this is third method,
Should be good point to implement this (pascal always has very simple
semantic and very strong type checking)
Of course you then you can use any enumerator with any collection, but
it will be better?
How many errors we then invoke?
Much less.
Best regards,
Paul Ishenin.
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