On 3/22/16 2:01 AM, Michael Van Canneyt wrote:
But you agree that if Find is called on an unsorted list, bogus data will
be returned ? Or, worse, an never-ending loop may occur ?
In short, as you say, an "error condition" can ensue without you
knowing it.
That is a bug. So, in my opinion (and of some others), Find is
implemented buggy in Delphi.
Consider the buggyness a given in what follows.
If we consider something a bug in Delphi, we do not copy the bug.
You happen to rely on this buggy behaviour. This is of course
unfortunate.
I attempted to fix this bug using a not too invasive method.
Originally I simply wanted to raise an exception, but that was deemed too
invasive.
There are now several options:
1. I change the code to raise an exception instead (as was my original
plan)
2. I change the code to resort to a linear search if sorted is false.
3. I introduce a boolean property that determines whether Find does
any check.
By default the check will be done, to warn people they're doing
something stupid. If they override the check, we can assume they
know what
they are doing.
4. Combine 1 and 3.
Or,
5. You override sort so it does nothing. It is virtual.
You can then set sorted to True, no sort will occur, and find will
do it's job.
6. You use another TStringList where you change find to suit your needs.
All it takes for you is to copy the implementation, you can keep
the same
name, and insert the unit after the classes unit in places where
you need it.
It's your call which of the 5 methods is used.
But one thing is sure: we're not reverting the behaviour back to the
buggy behaviour.
Michael.
_______________________________________________
fpc-devel maillist - fpc-devel@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
#1 is what Zoe Peterson (my coworker) has suggested as well. Without
that exception (as the code now is) there is no warning issued just an
ambiguous return of False. Which means that the code is still buggy as
the user could assume that the Index value points to next insert spot
and instead it is out of range and causes a crash. Setting Index value
to -1 would be a better indicator of bad usage than just returning False
(with raising an exception still being the best warning).
Keep in mind though that being able to call find on a manually sorted
list (Sorted <> true) is not buggy behavior (this is the Delphi
compatibility that we are interested in maintaining). In which case
adding in #3 would be necessary. So I guess I am for #4.
I would suggest that the added boolean flag be named to indicate that
the list is manually sorted (ManualSorted ?) rather than the flag being
just a 'bypass check' indicator. The check in Find would be "if not
Sorted or not ManualSorted then raise exception'. But that's just a
personal preference and not something that I feel extra committed to.
My second choice would be #1 by itself.
David
_______________________________________________
fpc-devel maillist - fpc-devel@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
