Are Objects really hard?

Hi guys,

Again one interesting topic for this weekend to discuss. David Nolen, a
Lisp and JavaScript guy posted in his blog an article titled Illiterate
Programming [1] where he said:

"...Yet I think Smalltalk still fundamentally failed (remember this is a
programming language originally designed to scale from children to
adults) because *Objects are really hard* and no-one really understands
to this day how to do them right...."

He links to Alan Kay post [2] back in 1998 where he talks about problems
with inheritance:

"Here are a few problems in the naive inheritance systems we use today:
confusions of Taxonomy and Parentage, of Specialization and Refinement,
of Parts and Wholes, of Semantics and Pragmatics..."

Let we concentrate on broader "Objects are really hard and no-one really
understands to this day how to do them right" claim and not merely
inheritance, please.

Best regards
Janko

[1] http://dosync.posterous.com/illiterate-programming
[2]
http://lists.squeakfoundation.org/pipermail/squeak-dev/1998-April/009261.html

--
Janko Mivšek
Aida/Web
Smalltalk Web Application Server
http://www.aidaweb.si

Well... functional programming is hard and not everybody really understands it... structured programming is hard and not everybody really understood it... hmm at the end, programming is hard :-)

I find the article rather kind to Smalltalk...

Illiterate programming = self literate programming...

Nicolas

2012/2/11 Janko Mivšek <[hidden email]>:

Let we remember that Smalltalk was designed for a kids, so "programming
is hard anyway" is in my opinion just too simplified answer.

While teaching new Smalltalkers I noticed that those without any
programming experience got it faster, specially comparing to those with
a relational DB experience. Who were and are still part of mainstream.

So, maybe it is better to say that established habits and mental models
in programmers heads never changed enough to get OO right?

To rephrase a bit differently: Hardly anyone is playing OO right because
OO was used too long on top of relational world and the ideas of pure OO
were forgotten and lost.

Best regards
Janko

S, Schwab,Wilhelm K piše:
--
Janko Mivšek
Aida/Web
Smalltalk Web Application Server
http://www.aidaweb.si

Janok

Frankly I do not care about what other people are thinking.
OOP is a success look at Java, C#.

Now let us keep our energy to build better Smalltalks.

Stef
On Feb 11, 2012, at 1:21 PM, Janko Mivšek wrote:

Hi Stef,

S, stephane ducasse piše:

> Frankly I do not care about what other people are thinking.
> OOP is a success look at Java, C#.
>
> Now let us keep our energy to build better Smalltalks.

Well, after hard work it is good from time to time to make a
retrospection and let our thoughts to think a bit broader, to look from
a distance to our work. To see the forest and not just trees.

So such debate from time to time is certainly refreshing and needed,
specially if it is started from a outsider's perspective. Every wise man
listen to the opinion of others. Well, of course wisely :)

In this case I see a wise thinking about weaknesses of OO and Smalltalk
and how to overcome it by better "best practices". For instance, the
newcommers are asking where to find a guidelines for modeling OO domain
models in pure OO way. In this guidelines we can emphasise above
mentioned best practices, then author's claim that  "no one really
understands to this day how to do them right" won't be valid much anymore.

Best regards
Janko


--
Janko Mivšek
Svetovalec za informatiko
Eranova d.o.o.
Ljubljana, Slovenija
www.eranova.si
tel:  01 514 22 55
faks: 01 514 22 56
gsm: 031 674 565

Indeed the article is kind to Smalltalk.

Janko wrote:

> In this case I see a wise thinking about weaknesses of OO and Smalltalk
> and how to overcome it by better "best practices". For instance, the
> newcommers are asking where to find a guidelines for modeling OO domain
> models in pure OO way.

The C++, Java and C# textbooks I read before I tried Smalltalk are not
very helpful.

I did not order a copy of Kent Beck's "Smalltalk Best Practice
Patterns" before if went out of print. Would it help?

It is hard to substitute many hours spent with time-tested Smalltalk
source code. Maybe an Active Essay (semi literate!) tourist guide to
the kernel and standard libraries would be a helpful learning tool.
Hypertext in source code (thanks to Ted Kaehler) still works.

http://wiki.squeak.org/squeak/42

Have fun! David

On Sat, Feb 11, 2012 at 08:08:33PM +0000, David Corking wrote:
>
> I did not order a copy of Kent Beck's "Smalltalk Best Practice
> Patterns" before if went out of print. Would it help?

Yes. Very worthwhile.

Dave

I agree with Hernan.  It's not Objects; it's software development in general that's hard.  Go work on a large project sometime, and witness the awesome that transpires in a large team best by *cough* process *cough*

On Feb 11, 2012, at 1:58 PM, Janko Mivšek wrote:

James Robertson
http://www.jarober.com
[hidden email]

Thanks bob
We are trying to improve on that front, but this is a battle of every moment. Now everybody can have an impact.
Join and help us building better libraries.

Stef

http://www.pharo-project.org

Milan zdravo!

S, Milan Mimica piše:

> Janko Mivšek
>
>     In this case I see a wise thinking about weaknesses of OO and Smalltalk
>     and how to overcome it by better "best practices". For instance, the
>     newcommers are asking where to find a guidelines for modeling OO domain
>     models in pure OO way. In this guidelines we can emphasise above
>     mentioned best practices, then author's claim that  "no one really
>     understands to this day how to do them right" won't be valid much
>     anymore.

> There are many books written on OO domain modeling and there is so much
> knowledge floating around.

Can you and others list some of those books and other useful resources?
Which are currently most popular, which are regarded as classical?

Maybe we can list them as recommended literature on our websites.

Best regards
Janko

> The claim that no one understands OO it just
> so stupid that it's not worth citing it. I for one do know how do it
> right, in any language. You don't even need an OO laguage. It has
> nothing do to with Smalltalk. It's about how you model real-life
> problems in code. I find it easy, straightforward and natural.
>
> --
> Milan Mimica
> http://sparklet.sf.net

--
Janko Mivšek
Aida/Web
Smalltalk Web Application Server
http://www.aidaweb.si

S, Milan Mimica piše:

>     Can you and others list some of those books and other useful resources?
>     Which are currently most popular, which are regarded as classical?
>
>     Maybe we can list them as recommended literature on our websites.

> Martin Fowler is my favorite. But there is a whole history of it,
> starting from GOF, or Christopher Alexander if you want. Again, it has
> nothing to do with Smalltalk in particular. You can do crappy
> architecture in Smalltalk just like you can in Java or C++.

I see many UML books around, so what is a state of UML modeling for
domain models in Smalltalk? Is anyone using it?

I have a feeling that Smalltalkers tend to avoid UML because of
complexity (it is complex, true), but it can be used pragmatically and
tailored to our use. Visualworks for instance have an nice UML class
editor called ADvance (see an example [1]), but it seems hardly anyone
use it.

At least class diagrams are very useful for documenting the domain
model. Just code is not enough. We are very weak here and maybe this is
a reason why people find Smalltalk hard. Because they are lost in all
that code, without any higher level picture.

Janko

[1] http://www.aidaweb.si/party-framework
--
Janko Mivšek
Aida/Web
Smalltalk Web Application Server
http://www.aidaweb.si

dcorking wrote

I did not order a copy of Kent Beck's "Smalltalk Best Practice

Great book, but the focus is on technique and I don't think it will help to grok what's special about OOP or Smalltalk. I would recommend "A Mentoring Course on Smalltalk" which goes way deep into how humans relate to the world around them and what that has to do with Smalltalk. Also, I've found it very valuable to read, and re-read, and re-read any relevant articles and papers from the PARC crew, especially Alan and Dan Ingalls. VPRI also has some good papers on their website.

HTH,
Sean

Hi all Smalltalkers!

Only cross posting to squeak and pharo (communities I know), because
this turned into a long post. But try reading it - I hope it is both fun
and perhaps interesting. :)

On 02/11/2012 01:21 PM, Janko Mivšek wrote:
As Hernan pointed out - it is programming that is hard, not *objects*
per se. While that is true, one can of course still reflect on the
aspects of OO and why people *perceive* it as hard.

SIDENOTE: As Milan wrote later in the thread - the patterns movement
that Kent Beck started together with the Gang of Four led to the
creation of TONS of books fully packed with OO designs in various
domains. So yes, there is an *abundance* of books on OO design to find
*iff* one goes looking for it.

> He links to Alan Kay post [2] back in 1998 where he talks about problems
> with inheritance:
>
> "Here are a few problems in the naive inheritance systems we use today:
> confusions of Taxonomy and Parentage, of Specialization and Refinement,
> of Parts and Wholes, of Semantics and Pragmatics..."

Of all OO mechanisms most agree that inheritance is the one that gets
abused the most... if we disregard the "abuse" one can find in so called
OO code that stems from it not being OO at all :)

Alan writes "confusions" and I suspect he carefully avoids saying one is
wrong and the other is right, because its not that simple. Truth is one
can use inheritance differently - as long as it makes your life better
it can't really be argued to be "wrong". :)

I think most OO developers goes through some "ladder of enlightenment"
going something like this:

0. You really have no clue and tend to confuse composition "parts and
whole" with inheritance. You just create a mess. Perhaps you avoid this
mess by reading a book or attending an OO course, but hey, who does that
in 2012? ;). But let's say you *do* read a book - proceed to level 1...

1. You get all into Animals and other "inheritance" examples mirroring
the real world. Perhaps you get totally sucked into the "mirror the real
world"-idea. Thus, you try desperately to find "ISA" relations among the
domain objects and use those for inheritance, without really thinking
*why* that is a good idea. And sure, it often gets it fairly right so
it's a huge step forward. But let's pretend you now have coded quite a
bit and thus proceeds to level 2 :)

2. Specialization. After some time you start to understand polymorphism
and the substitution principle etc, so instead of blindly testing if "A
isa B" sounds right in your ears you start thinking in terms of
generalisation and specialization. And you see objects in your head. You
talk about them as if they are concrete and you can hold them in your
hand etc. Perhaps you even draw them on whiteboards and envision them in
different scenarios "talking to each other". If you use a statically
typed language this is where your road stops :). You end up writing
fairly good code, but your inheritance will probably be totally focused
on enabling polymorphism between objects, which of course is not all
bad. But hey, after a few years of Smalltalking - proceed to level 3.

3. As a seasoned Smalltalker you eventually come down from your "OO
rush" and realize that... hey, wait a minute! Polymorphism is not *tied*
to class inheritance (unless you are trapped in some static type
system). In fact, you realize that class inheritance in Smalltalk is
"merely" a nice way of reducing the redundancy of code by creating
dependencies between separate abstractions of code. This realization
enables you to use inheritance in a more liberal fashion - which
probably means you tend to use it *less*. And instead you tend to "add
more objects" and use composition of objects more and more, relying on
brittle deep hierarchies of inheritance less and less.

SIDENOTE: A really cool example of how powerful object composition is:
PetitParser by Lukas. For years we have been creating parsers by
generating code from specifications and suddenly Lukas decides that hey,
why not instead *compose* a parser from ...objects? It is so obvious in
retrospect, but the result is a tremendously nicer and more powerful way
of constructing parsers.

You also conclude that while you *can* reuse behaviors and compose
behaviors using inheritance you are also aware that inheritance creates
a life cycle *dependency* between classes that you *may* or *may not*
want to have. Class inheritance is a brittle relation. Thus, even if
class A *can* inherit from B, you might decide not to - because you
anticipate that the development lineage will diverge, or perhaps you
have no control over A (library? other developer? bad code?), and you do
not want that dependency. But the up side is that sometimes you *really*
want that dependency, change superclass and bam - affect all subclasses.

Another obvious benefit of inheritance is of course "documentation
structure" that you and other developers can understand.

...well. Of course, the above was written sloppily and can of course be
refined or totally shot down. Feel free to do both! :)

regards, Göran

PS. Why oh why did Pharo lose the "double click on ? in the class
browser to see inheritance textually"-mechanism? :)

2012/2/13 Göran Krampe <[hidden email]>:
Well, we like to look at Java and hold our noses, but really, Java has
a rubbish type system, regardless of it being static. Now if you were
looking at some Haskell code, you'd see some highly polymorphic stuff
going on thanks to typeclasses. And in the dynamic functional language
corner you'd recognise good Smalltalk practice in Clojure's Protocols.
(They like to say that protocols solve the Expression Problem, but
really, it's multimethods that do that, not protocols.)

If you'd like to see Clojure's protocols in action, this is a nice
demonstration: http://news.ycombinator.com/item?id=3515862

The thing to bear in mind here is that (a) protocols won't surprise
you; they're "this thing responds to this set of messages" just as
you'd expect and (b) they do not pollute the global namespace: you can
add a method to some object _in a scoped manner_.

> SIDENOTE: A really cool example of how powerful object composition is:
> PetitParser by Lukas. For years we have been creating parsers by generating
> code from specifications and suddenly Lukas decides that hey, why not
> instead *compose* a parser from ...objects? It is so obvious in retrospect,
> but the result is a tremendously nicer and more powerful way of constructing
> parsers.

But you realise the irony here, right? That if you google "parser
combinator" you hit all those "non-OO" languages like Haskell (and
then the new kids like Scala and F#). (Yes, yes, 3rd hit's Gilad's
talk. Not surprising.) But then, that in itself isn't terribly
surprising, because not many people get at a deep level that objects
are nothing more than higher order functions that close over
variables.

I have a long-running argument with a colleague who says (among other
reasons) that he thinks Smalltalk is rubbish because class-based
systems are rubbish (because of all the issues around inheritance).
But, of course, while we happen to use classes all the time, we don't
HAVE to. And, indeed, there are several prototype-based Smalltalk
libraries. Because, at its core, Smalltalk isn't about classes, it's
about objects sending messages to each other.

> You also conclude that while you *can* reuse behaviors and compose behaviors
> using inheritance you are also aware that inheritance creates a life cycle
> *dependency* between classes that you *may* or *may not* want to have. Class
> inheritance is a brittle relation. Thus, even if class A *can* inherit from
> B, you might decide not to - because you anticipate that the development
> lineage will diverge, or perhaps you have no control over A (library? other
> developer? bad code?), and you do not want that dependency. But the up side
> is that sometimes you *really* want that dependency, change superclass and
> bam - affect all subclasses.

Indeed: you should probably only use inheritance if you _have to_.
Exactly because it couples every class in an hierarchy together, and
you can no longer understand a method without understanding how that
method overrides/replaces/is overridden/is replaced in the tree.

> Another obvious benefit of inheritance is of course "documentation
> structure" that you and other developers can understand.

I'm sure we can do much better though. I'm thinking here of "this is a
Stream because it understands <set of standard Stream messages>".

frank

> ...well. Of course, the above was written sloppily and can of course be
> refined or totally shot down. Feel free to do both! :)
>
> regards, Göran
>
> PS. Why oh why did Pharo lose the "double click on ? in the class browser to
> see inheritance textually"-mechanism? :)
>

On 13 Feb 2012, at 10:23, Göran Krampe wrote:

> PS. Why oh why did Pharo lose the "double click on ? in the class browser to see inheritance textually"-mechanism? :)

I just tried in my 1.4 image #14329 image with the standard browser and it works:

ProtoObject #()
        Object #()
                Magnitude #()
                        LookupKey #('key')

                                Association #('value')

Sven

Hi Göran,

Göran Krampe wrote:
There is a mistake in this discussion right from the start that nobody
pointed out. When Alan says "Nobody knows how to do objects right" he's
not talking about programing in an OO language, but about designing the
language and system itself. I agree with this. I prefer Smalltalk to all
the systems/languages done afterwards, trying to fix Smalltalk
weaknesses. Besides, he praised many times the works of members of his
various teams, and of members of this community.

WRT the usual comment, saying that it is hard to program well with
objects and that this implies that objects are bad, is like saying the
guitar is bad because it is not easy to play it really well. I took ten
years of piano classes when I was a kid, but I'm not good enough to play
in public, and I guess I'll never be. I'm not talented enough for that.
The same can happen to others with programming, and with objects in
particular. If the player is not good, it is not the instrument to blame!

Or praised. Very well said, Göran!

Cheers,
Juan Vuletich

> regards, Göran
>
> PS. Why oh why did Pharo lose the "double click on ? in the class
> browser to see inheritance textually"-mechanism? :)
>

There is no question that over-use of inheritance (failure to understand composition) is a classic beginner mistake.  That said, don't underestimate the value of inheritance.  Granted, the example I have in mind is perfect for specialization, but beyond that, failure to use (extensive) inheritance can at times lead to lots of duplicate code (which is really bad).  Say it once - inheritance can help one do just that (policy up, implementation down, etc.).

Bill

On 02/13/2012 12:22 PM, Sven Van Caekenberghe wrote:
>
> On 13 Feb 2012, at 10:23, Göran Krampe wrote:
>
>> PS. Why oh why did Pharo lose the "double click on ? in the class browser to see inheritance textually"-mechanism? :)
>
> I just tried in my 1.4 image #14329 image with the standard browser and it works:

Oh nice! I confess i didn't try the latest Pharo (only 1.2) before I
wrote this - I just presumed it still did not work ;) My bad.

regards, Göran