Harvesting Float Interval - questionable feature

Playing with Interval, here is a report and some questions about a
special feature

INTRODUCTION:
------------

Interval on Float are messy.
#do: loops are not consistent with #size nor #at: because of accumulated
round off errors.
This is because inside the do loop we write
        aValue := aValue + step
And stop the loop when we reach stop

Things are better if we make things compatible with #at: (index is 0-based)
        aValue := start + (index * step)
And stop after self size iterations to be compatible with #size

All this is at http://bugs.squeak.org/view.php?id=6456
It has the advantage of also solving #reverseDo:
http://bugs.squeak.org/view.php?id=6438.

Another related stuff is the way we test for inclusion.
Current implementation try to test inclusion with a fuzzy tolerance.

Unfortunately, it is completely broken and have incorrect patch at
http://bugs.squeak.org/view.php?id=1602 for speeding up indexOf: as
noted by german morales, and better patch by boris gartner at
http://bugs.squeak.org/view.php?id=1603 for correcting both includes:
and indexOf:

The patch is however incomplete because it handles only approximate by
excess, not by default as shown in http://bugs.squeak.org/view.php?id=6455.

QUESTION:
--------

But why do we test for Float inclusion with fuzzy tolerance in Interval
and not in other collections? And why a fixed tolerance? (1.0e-10
relative to step in original, 1.0e-8 in some correction).
I would tend to implement exactly same behaviour as super and eventually
implement a includes:withTolerance: if needed, in all Collection (though
  this is as simple as #detect:, it might be accelerated in Interval if
there is a dedicated selector).

My feeling is that previous implementation of do: and unconsistency with
at: might have motivated the fuzzy test.
But is there another reason to make Interval behave differently from super?

I tend to be cautious now, because when i tried to correct first and
last that incorrectly handle empty Interval
(http://bugs.squeak.org/view.php?id=6454), it did break the image.
Text selection rely on this behaviour and that is more than 10 messages
to patch.

What is your opinion about the fuzzy inclusion?

2007/4/30, nicolas cellier <[hidden email]>:
> What is your opinion about the fuzzy inclusion?

You are probably the only expert for that domain :-)

--
Damien Cassou

Damien Cassou a écrit :
> 2007/4/30, nicolas cellier <[hidden email]>:
>> What is your opinion about the fuzzy inclusion?
>
> You are probably the only expert for that domain :-)
>
Very kind. I hope not.
Squeak floats were written well before i ever got interested in.
My job is limited to some polishing.

And my question is about thoughts behind current implementation and
eventual use in some application, both beyond my expertise.

That's a general problem in Squeak (and sure in other open source projects):
- why this implementation ?
- why this feature ?
It's not written in the code, as legible as it can be.
It could eventually be in SUnit TestCase with good comments.
Unfortunately, the answer is often only in the mind of few persons.
But i don't want to open a thread on documentation again...

Nicolas