[fpc-pascal] private integer is an illegal counter variable
jonas.maebe at elis.ugent.be
Fri Nov 27 15:56:21 CET 2009
On 27 Nov 2009, at 15:49, Juha Manninen wrote:
> If I define a private integer:
> TDemo = class(TCustomApplication)
> i: integer;
> and in a protected method I use it:
> for i := 0 to List.Count - 1 do
> then I get an error:
> Error: Illegal counter variable
> Moving it to method's var section helps.
> Method's var section is also better place for it in general, but
> still it
> should be legal to use a private member as counter var.
The reason is that a for-loop tries to make a number of reasonable
guarantees that the counter variable cannot be modified during the
loop. E.g., direct assignments to a counter variable are forbidden
inside the loop (except in TP-mode). If you use a private field, then
any method of that class called in the body of the loop can easily
(accidentally) change the value of the counter variable, completely
messing up the loop.
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