[Caml-list] OCaml and Design Patterns

[Caml-list] OCaml and Design Patterns

[Vasili Galchin]

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Hello,
 
     I am working on a C++ project (hey I have to make money ... I personally hate the language) so I am using Design Patterns. In the standard GoF book (Gang of Four design pattern book), the authors say that some patterns already exist (builtin) in some languages. What design patterns do you think would be useful if I am using the OO features of OCaml (i.e. non-pure functional features)?
 
Thanks, vasili

		
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Re: [Caml-list] OCaml and Design Patterns

[Richard Jones]

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On Wed, Oct 20, 2004 at 10:13:01AM -0700, Vasili Galchin wrote:
> Hello,
>  
> I am working on a C++ project (hey I have to make money ... I
> personally hate the language) so I am using Design Patterns. In the
> standard GoF book (Gang of Four design pattern book), the authors say
> that some patterns already exist (builtin) in some languages. What
> design patterns do you think would be useful if I am using the OO
> features of OCaml (i.e. non-pure functional features)?

Just my personal opinion, but I've seen a lot of terrible code written
which uses "design patterns" ...  A lot of the patterns seem to exist
solely to bypass problems with OO languages.

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
Merjis Ltd. http://www.merjis.com/ - improving website return on investment
"One serious obstacle to the adoption of good programming languages is
the notion that everything has to be sacrificed for speed. In computer
languages as in life, speed kills." -- Mike Vanier

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Re: [Caml-list] OCaml and Design Patterns

[David Brown]

On Wed, Oct 20, 2004 at 06:30:01PM +0100, Richard Jones wrote:

> Just my personal opinion, but I've seen a lot of terrible code written
> which uses "design patterns" ...  A lot of the patterns seem to exist
> solely to bypass problems with OO languages.

Design Patterns seem very similar to what is usually called idioms in other
languages.  They're just common constructs you learn for common tasks.  An
example in ocaml might be typical recursion for a loop.

However, the OO Design Patterns do seem more to be techniques used to
compensate for defects in the OO methodology, or specific languages.

I would suspect that when someone encounters a place to use a design
pattern in OCaml, the problem would much better be solved by using some
other feature of the language.

Dave

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Re: [Caml-list] OCaml and Design Patterns

[Brian Hurt]

On Wed, 20 Oct 2004, David Brown wrote:

> On Wed, Oct 20, 2004 at 06:30:01PM +0100, Richard Jones wrote:
> 
> > Just my personal opinion, but I've seen a lot of terrible code written
> > which uses "design patterns" ...  A lot of the patterns seem to exist
> > solely to bypass problems with OO languages.
> 
> Design Patterns seem very similar to what is usually called idioms in other
> languages.  They're just common constructs you learn for common tasks.  An
> example in ocaml might be typical recursion for a loop.
> 
> However, the OO Design Patterns do seem more to be techniques used to
> compensate for defects in the OO methodology, or specific languages.
> 
> I would suspect that when someone encounters a place to use a design
> pattern in OCaml, the problem would much better be solved by using some
> other feature of the language.
> 

I don't seem to have quite as negative a view of the GoF book as many 
people around here seem to.  But I think this is because I see design 
patterns as a more general idea than just what the GoF presented- and I'd 
argue this view is supported by the pattern community- as now you have 
software architecture patterns, anti-patterns, etc.  I think there are OO 
patterns (which is what is documented in the GoF book), functional 
patterns, even procedural patterns.

I also think that the difference between idioms and patterns is mainly a
matter of degree- they're all of a kind, if you see.

Note that there are a number of Functional patterns which are for working 
around the limitations of the Ocaml language as well.  An example I'll 
hold up here is "build a list backwards, then reverse it" pattern, to make 
a function tail recursive.  Others are less clear cut- is "return the 
update applicative structure" a work-around, or a better way of doing 
things?

The point I'd like to make to the original poster is that the GoF isn't 
the last word on how to think about problems, especially not in Ocaml.  
Look for the new patterns Ocaml allows/encourages.

-- 
"Usenet is like a herd of performing elephants with diarrhea -- massive,
difficult to redirect, awe-inspiring, entertaining, and a source of
mind-boggling amounts of excrement when you least expect it."
                                - Gene Spafford 
Brian

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Re: [Caml-list] OCaml and Design Patterns

[Vasili Galchin]

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Richard Jones <rich@annexia.org> wrote:
On Wed, Oct 20, 2004 at 10:13:01AM -0700, Vasili Galchin wrote:
> Hello,
> 
> I am working on a C++ project (hey I have to make money ... I
> personally hate the language) so I am using Design Patterns. In the
> standard GoF book (Gang of Four design pattern book), the authors say
> that some patterns already exist (builtin) in some languages. What
> design patterns do you think would be useful if I am using the OO
> features of OCaml (i.e. non-pure functional features)?

Just my personal opinion, but I've seen a lot of terrible code written
which uses "design patterns" ... A lot of the patterns seem to exist
solely to bypass problems with OO languages.
^^^^ Rich, in the case of C++ I would totally agrere with you!

Vasya


Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
Merjis Ltd. http://www.merjis.com/ - improving website return on investment
"One serious obstacle to the adoption of good programming languages is
the notion that everything has to be sacrificed for speed. In computer
languages as in life, speed kills." -- Mike Vanier


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Re: [Caml-list] OCaml and Design Patterns

[Vasili Galchin]

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Richard Jones <rich@annexia.org> wrote:
On Wed, Oct 20, 2004 at 10:13:01AM -0700, Vasili Galchin wrote:
> Hello,
> 
> I am working on a C++ project (hey I have to make money ... I
> personally hate the language) so I am using Design Patterns. In the
> standard GoF book (Gang of Four design pattern book), the authors say
> that some patterns already exist (builtin) in some languages. What
> design patterns do you think would be useful if I am using the OO
> features of OCaml (i.e. non-pure functional features)?

Just my personal opinion, but I've seen a lot of terrible code written
which uses "design patterns" ... A lot of the patterns seem to exist
solely to bypass problems with OO languages.
^^^^ Rich, in the case of C++ I would totally agrere with you!

Vasya


Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
Merjis Ltd. http://www.merjis.com/ - improving website return on investment
"One serious obstacle to the adoption of good programming languages is
the notion that everything has to be sacrificed for speed. In computer
languages as in life, speed kills." -- Mike Vanier


> ATTACHMENT part 2 application/pgp-signature name=signature.asc



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Re: [Caml-list] OCaml and Design Patterns

[pad]

Vasili Galchin <vasiliocaml@yahoo.com> writes:

> Hello,
>  
>      I am working on a C++ project (hey I have to make money ... I
>      personally hate the language) so I am using Design Patterns. In
>      the standard GoF book (Gang of Four design pattern book), the
>      authors say that some patterns already exist (builtin) in some
>      languages. 

yes, have a look at :
 http://www.norvig.com/design-patterns/


> What design patterns do you think would be useful if
>      I am using the OO features of OCaml (i.e. non-pure functional
>      features)?

I don't really understand the question because in theory all the design pattern are useful.
So abstract factory can be useful in O'Caml too.
Stragegy is useful too but easier in O'Caml since higher order function allow
to encode easily the strategy pattern.
There is discussion in the O'Caml manual about the observer pattern at:
 http://caml.inria.fr/ocaml/htmlman/manual007.html
 (section 5.3)

Hope it helps.


>  
> Thanks, vasili
> 
> 		
> ---------------------------------
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> vote.yahoo.com - Register online to vote today!

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Re: [Caml-list] OCaml and Design Patterns

[pad]

Brian Hurt <bhurt@spnz.org> writes:

> On Wed, 20 Oct 2004, David Brown wrote:
> 
> > On Wed, Oct 20, 2004 at 06:30:01PM +0100, Richard Jones wrote:
> > 
> > > Just my personal opinion, but I've seen a lot of terrible code written
> > > which uses "design patterns" ...  A lot of the patterns seem to exist
> > > solely to bypass problems with OO languages.
> > 
> > Design Patterns seem very similar to what is usually called idioms in other
> > languages.  They're just common constructs you learn for common tasks.  An
> > example in ocaml might be typical recursion for a loop.
> > 
> > However, the OO Design Patterns do seem more to be techniques used to
> > compensate for defects in the OO methodology, or specific languages.
> > 
> > I would suspect that when someone encounters a place to use a design
> > pattern in OCaml, the problem would much better be solved by using some
> > other feature of the language.
> > 
> 
> I don't seem to have quite as negative a view of the GoF book as many 
> people around here seem to.  But I think this is because I see design 
> patterns as a more general idea than just what the GoF presented- and I'd 
> argue this view is supported by the pattern community- as now you have 
> software architecture patterns, anti-patterns, etc.  I think there are OO 
> patterns (which is what is documented in the GoF book), functional 
> patterns, even procedural patterns.

I totally agree with you.
In fact the haskell community have developped design patterns at:
  http://www.haskell.org/hawiki/CommonHaskellIdioms

They have adapted the idea of GoF to push it further cos in functionnal langage the main
ideas of the GoF book were already known/used by the fp community.



> 
> I also think that the difference between idioms and patterns is mainly a
> matter of degree- they're all of a kind, if you see.
> 
> Note that there are a number of Functional patterns which are for working 
> around the limitations of the Ocaml language as well.  An example I'll 
> hold up here is "build a list backwards, then reverse it" pattern, to make 
> a function tail recursive.  Others are less clear cut- is "return the 
> update applicative structure" a work-around, or a better way of doing 
> things?
> 
> The point I'd like to make to the original poster is that the GoF isn't 
> the last word on how to think about problems, especially not in Ocaml.  
> Look for the new patterns Ocaml allows/encourages.

People generally disrespect the work done by other communities (and then
reinvent it giving it another name).

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[Caml-list] ocamaweb release 6.01

[charles@laposte]

A new version (6.01) of OCAMAWEB is available at sourceforge :

http://sourceforge.net/project/showfiles.php?group_id=66639

It's a litterate programming tool written in ocaml and that can be used on  
any language having comment marks of one character (I deeply think about  
an upgrade to *any* language).
It is used for more that 2 years at MIRIAD Technologies, where it is used  
to comment algorithmic code.
config files exist for awk and r-project languages, and I will soon tune  
one for the SAS macro programming language.

feel free to use, read and comment the code (It is based on my first ocaml  
experience, so I know that I should build a fully new version as soon as  
possible : advices are welcome...).

charles

-- 
Charles-Albert LEHALLE
charles@lehalle.net
keyserver: http://pgp.mit.edu/
Such is the advantage of a well constructed language that its simplified  
notation often becomes the source of profound theories.
  In N. Rose
de Laplace, Pierre-Simon (1749 - 1827) In Mathematical Maxims and Minims,  
, Raleigh NC:Rome Press Inc., 1988.

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Re: [Caml-list] ocamaweb release 6.01

[David Brown]

On Thu, Oct 21, 2004 at 12:31:36PM +0200, charles@laposte wrote:

> It's a litterate programming tool written in ocaml and that can be used on  
> any language having comment marks of one character

In other words, it can't be used with Ocaml, C, C++, Java, Ada, Haskell?
So it is a literate tool for scripting languages such as sh, perl and
python?

Dave

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Re: [Caml-list] ocamaweb release 6.01

[lehalle@miriad]

On Thu, 21 Oct 2004 10:12:48 -0700, David Brown <caml-list@davidb.org>  
wrote:
>> any language having comment marks of one character
> In other words, it can't be used with Ocaml, C, C++, Java, Ada, Haskell?
> So it is a literate tool for scripting languages such as sh, perl and
> python?

MATLAB, SAS and S-plus were the target of OCAMAWEB (for signal processing  
and probability/statistics algorithms prototyping, in which it is very  
valuable to include mathematical proofs into code), so I at the time I  
developed ocamaweb, I did not think that it could be usefull for the  
languages you cite.
Now that a lot of people use ocamaweb outside of MIRIAD, I will have to  
extend it to any language...

Anyway, from my point of view, there is a lot of tools to comment code a  
proper way (doxygen, ocamldoc, etc), and a lot of programming tasks do not  
need "real" litterate programming (in java for instance, a "linear"  
documentation tool like javadoc is mainly efficient).
The point is that when you develop code that implement some mathematical  
results you obtain and when you want to share that code (and the  
mathematics that support it) with other people (that's our case inside  
MIRIAD), you need to be able to "reconfigure" your code to produce a  
documentation including mathematical glyphs (using LaTeX is a good option)  
: that's what ocamaweb allow to obtain. And a lot of people implement such  
mathematical "adjustments" of existing results in signal processing and  
statistics / probability ; those people mainly use MATLAB, S-plus (or R)  
and SAS.

So ocamaweb primary goal is definitely not to comment sh, perl or awk  
(even if now that it is on my computer, I use it with those languages) ;  
it's to produce restructured documentation including mathematical proofs.

charles

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