Re: SOLVED! Decoupled Mutual Recursion Challenger

[jgv@swl.msd.ray.com (John Volan)]

Robb.Nebbe@di.epfl.ch (Robb Nebbe) writes:

>As an analogy consider a wall as representing a programming problem
>and a language as providing a way to get to the other side. What you
>have seen is a lot of "ugly workarounds" to go through the wall.
>I saw at least one suggestion to go over the wall and another to
>go around the wall but both were refused. Why? because the goal
>had ceased being "getting to the other side" but instead had become
>"going through the wall".

Well, Robb, the goal (in my mind) was always to get *through* the
wall, not to go around it.  Several folks misunderstood my question to
be how to get around the wall, but, at least for me, the goal didn't
"cease" to be one thing and turn into another.  Also, to be fair, I
didn't really "reject" those alternatives, I merely said that they
didn't meet my goal.  I think that I was careful to accept those
alternatives for what they were worth: They are useful for certain
applications (but not perhaps the application I had in mind).  I agree,
sometimes, for some applications, all that is needed is a sidewalk.

>- Robb Nebbe

>P.S. the fact that some langauges provide a tool that will cut a
>hole in the wall and install a door to the otherside may lead
>some to believe that it is a good idea to go through the wall.
>They must first answer the question "Why was the wall there in
>the first place?"

Ah, well, that is an interesting question.  If the wall truly serves
no purpose, then yes, I could see how going around it, or climbing
over it, or even demolishing it entirely, would be preferable to
taking the trouble to cut that hole and install that door.

But what if the wall were the side of a *building*?  Such a wall
serves a very definite purpose: It separates the interior of the
building from everything exterior to it, including things like weather
and wild animals.  It also separates the building from all the other
buildings in the city.  

If one's goal is to find a convenient way to get *inside* the
building, and not simply to take a stroll around it, then it is
pointless to suggest going "around" the wall.  Certainly, it is even
more ridiculous to suggest climbing *over* the building!  But I think
the proprietors of the building would be a tad miffed if one were to
suggest *demolishing* the wall.  And, in a large city full of
buildings, I don't think it is practical to suggest eliminating all
walls entirely simply because the citizenry need to be able to go from
one establishment to another in the course of their daily business.
Luckily, "arcologies" are still stuff of science fiction, or the
fevered dreams of former Soviet city planners.  No, one just has to
face the fact that walls are occasionally very valuable things, and
having a door in the middle of a wall might just be exactly what is
wanted.  Especially if it's strategically placed to offer convenient
access to those who have legitimate reasons for entering and exiting
the building, but properly guarded against those who do not.

Now, if your building material (programming language) is a relatively
flimsy substance such as paper or rawhide or canvas, it may be quite
easy to take a knife and cut yourself a nice, serviceable door-flap
any time you want.  On the other hand, if your wall is made of wood or
brick or concrete, then yes, it does take a bit of sweat to saw or
drill yourself a hole.  Some folks who are used to roughing it in the
wild in tents (and damn proud of it too!) might find all that effort
ludicrous.  A few of those folks might even suggest the use of
dynamite -- but results are not guaranteed.  

However, there may be other people in this world who have learned how
to work with stronger materials, and who are appreciative of having a
nice, sound roof over their heads when the weather gets rough.  Such
people might not see the effort of cutting the hole as a waste at all.
In fact, being conscientious civil engineers, they might even take the
trouble to finish off the edges of the hole, install a lintel,
baseplate, and hinges, mount the door, and, as an added courtesy to
the client, include a doorknob and a deadbolt.  Is that an "ugly
workaround"?  Only if it leaks in the rain!

Analogies are lovely things, but they can be double-edged swords :-)

--John Volan

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