Re: The state of functional programming

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Thu, 29 Jul 2010 15:20:48 +0000 (UTC), Warren wrote:

> Dmitry A. Kazakov expounded in
> news:1oubrlamjqe8q$.bdwkb9i7ys6b$.dlg@40tude.net: 
> 
>> On Wed, 28 Jul 2010 19:09:17 +0000 (UTC), Warren wrote:
>> 
>>> Each collection of languages best solve problems in their 
>>> domain of applicability.
>> 
>> That reminds me someone's saying about 5GL in early 90's: "if 5GL is
>> an answer what was the question?"
>> 
>> What are the domains of poor languages? Since they must exist, 
> 
> Perl ;-)
> 
>>> For my money, FP still is less generally effective because
>>> it relies on special tricks/algorithms to narrow down the
>>> huge number of paths for a solution.
>> 
>> This universally applies to all declarative languages.
> 
> I think you missed my point - perhaps it wasn't expressed
> clearly.
> 
> As I understand it, a FP tries to determine conclusions 
> from a universe of facts, given some inputs. For smaller
> problems this can be _exhaustively_ analyzed and results 
> obtained.

And so does any declarative language. You declare some facts in whatever
form (as relations, as connections of blocks etc, for that matter, as types
in a strongly typed languages like Ada). The system infers from them some
executable code.

> However for more "practical" sized problems (we could argue
> what "practical" sized problems are), the number of "things"
> that must be analyzed becomes huge - taking 'forever' to 
> solve. To counter this, existing FP technologies use 
> special tricks for reducing the number of "things" to be 
> considered. 

Same with all others.
 
> The problem with this approach is that some problems 
> then won't lead to a solution because some of the paths 
> that may have lead to a solution were eliminated. Another
> side effect of this is that it may lead to suboptimal
> conclusions (the better possibilities were eliminated).

Furthermore some declarative frameworks are weaker than TM. I.e. whatever
corpus of facts you take you would be unable to infer what you can using an
imperative language.

> The "problem set size" issue, as I understand it, is still
> the main area of intense research in FP. But as it sits
> presently, the issue is still essentially unsolved. 
> 
> Some big improvements (special algorithms) have been 
> developed over the years to make FP more practical, 
> but in essence that same basic problem still exists.

I think that the main problem of all domain-specific languages is that, in
contrast to the acclaim, they aren't built around a domain. They are about
a class of some well studied methods. This class is them promoted as the
"domain."

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de