terminological obscurity

[Donn Cave]

Quoth Arthur <ajsiegel at optonline.com>:
| >
|>  Consider use of tuples such as (hostname, port) or (firstname, lastname, 
|>  middleinitial) or (x_coordinate, y_coordinate). In all cases you *know* 
|>  what the first element means, what the second element means etc. It is 
|>  usually not useful to find a value since the different values mean 
|>  different things. You might rather do this something like - if host_port[1] 
|>   == 80:... 
|>
|> Can you quote _both paragraphs_ of the above and point out the
|> circularity in his explanation?
|
| Given a tuple (1,1,1) representing  X,Y,Z corrdinates, I - for one -
| have trouble explaining the heterogenous nature of the data, outside
| of the "tuple" sense of the word. 

I don't know what you mean by `outside the "tuple" sense of the word",
but in a way I think that may be nearly the problem.  Of course if you
consider these objects on their own, the contents of the tuple but
isolated from that context, they're as homogeneous as you could want,
in fact they would be the very same object.

But (I hope) no one articulating this point of view says "homogeneous
data", or "homogeneous contents", etc.  Of course the very same objects
could occur in two separate sequences, one homogeneous and the other
heterogeneous.  This point is that the tuple itself is heterogeneous,
each element having a separate non-interchangeable role;  the list is
homogeneous, having at most some sort order.  The objects don't express
this on their own, it's a property of the sequence.

|> I don't know if homogeneity is the most useful term to get at the
|> distinction as I understand it, but evidently that's how Guido tried
|> to explain it, so that's where we start.  It can take some explaining.
|> We could try to think of better ways to approach it - maybe bring in
|> the notion of a tuple as a "product" of its elements - but the parties
|> to that discussion would have to 1) understand the distinction, and
|> 2) not be satisfied with the way it's currently explained.  No sign
|> of anyone in that corner yet.
|
| The best reason to describe the current explanations as a tautology,
| is precsiely because it can only really be understood as a meaningful
| explanation to those who don't really need one.  It does little, in my
| opinion, to serve as help for those who might.

Well, I don't know if anyone really needs an explanation, and I'm
struggling with my understanding of "tautology" to fit it in here,
but there is something to what you say.  It's kind of a Python nerd
topic, not a key that's going to unlock the waiting potential of the
language.

But for me, I know I didn't get it on my own at first.  I tended to
use tuples as a `more efficient' sequence type.  I think the impetus
to reform my thinking came from here, and I think nerd chatter like
this does serve some purpose.

	Donn Cave, donn at drizzle.com