Michael Van Canneyt wrote:
And what is so special in the class type?
First:
For a for loop, you are guaranteed that the loop logic behaves correctly.
A loop is equivalent to the following:
I:=StartValue;
E:=EndValue;
While I<=EndValue do
begin
// loop stuff
Inc(I);
end;
And you cannot change I manually during the loop.
You don't know this with an iterator since you depend on the implementation
of the iterator. The loop could loop forever then...
Yes. For-in loop is not a for-to loop. While and Repeat loops can also
loop forever. You can't protect a developer if his hands grow from the
wrong place.
Secondly:
You promote a certain class/interface to a language feature. The
compiler then depends on the presence of a certain class with some
'known' methods in the RTL.
Yes, I see this very bad too. That's why this discussion is started. But
what can be suggested instead?
Maybe new type?
TSomeIterator = iterator(<iterated type>)
...
end;
or we can use some basic class:
TIterator = class
public
function MoveNext: Boolean;
property Current: <what type to return?>
end;
I don't like non-constructive criticism. If you don't like something
please be ready to suggest something instead. And in this case something
what can be used to implement for-in loop for classes and implements
this delphi compatible (so 'for S in MyStringList do' will work).
Best regards,
Paul Ishenin.
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