Am 04.08.15 um 00:22 schrieb webwarrior:
We're drifting too much into philosophy here. Meaning of this, meaning
of that...
Thanks. I'd love to be clever enough to be a philosopher.
I'd argue there is no intrinsic meaning in statements such as "string A
is less than string B". But it is useful to have order defined on set of
words and character strings in general. Lexicographic order has some
useful properties and has been used in dictionaries for a long time.
The only thing I am worried about here is that you use the word
"intrinsic".
Other than that, you are fully correct. In daily life, we've grown
accustomed to a being the letter before b. Not intrinsically, but
practically.
Not sure what exactly this has to do with Collections that hold any kind
of objects.
Please implement comparison and move it to the Pharo base library,
because, since there is no intrinsic meaning to comparing collections
anyway, you can do whatever you want, as long as it is well-defined and
it can be overridden if needed. Just because I am saying this is pollution
and questionable, you shouldn't keep yourself from doing so.
Now nobody (OK, maybe I'm exaggerating a bit) questions whether strings
should have comparison and what ordering to use. We can easily
generalize this to all sequences with elements that can be compared -
and that's what designers of programming languages did. So it became
like de facto standard.
Note that default lexicographic ordering for strings is not always
desired - e.g. some file browsers have option of "numerical order"
(which accounts for numbers - "10" comes after "9" and so on). Still
it's not a reason to abandon default ordering.
Oh, now it's you who drifts into philosophy. You just said it's well
defined and therefor okay to have some default ordering. Now daily life
jumps in and jumps onto your fine arguments and breaks everything.
And then, the whole Unicode catastrophe around differences between
languages and cultures just shows that oversimplifying can be expensive
errors. You say nobody questions if A<B, admitting it may be
exaggerating. In reality there are several billions of people on the
planet who wouldn't really care because neither A nor B are used in
their mother language. This, of course, is philosophocal and I apologize
immediately.
My point is that lexical ordering is business logic, and we currently
see what a mess we made when we decided to use the roman alphapet
exclusively for lexical ordering. We just locked out 40-50% of the human
race from having any meaning in ordering. Maybe lexical ordering should
be pluggable, just because it is not intrinsic. Because the order of
things is often dependent on context. And context is something that is
not well suited for a base class library if it is not designed as
something extendible/configurable.
I admit I am at the edge of philosophy here, because what the heck does
this "oh, the chinese use pictures instead of letters" have to do with
an abstract definition of comparison between collections?
On a side note: some functional programming languages with ADTs
(algebraic data types) automatically provide structural equality and
comparison for all ADTs, including user-defined, where it is possible.
And it's awesome, because it saves you from writing boilerplate code.
Again, you could say that there is no meaning in comparison of, say,
some n-ary trees of bools. But it has practical use: a datatype must
implement comparison to be used in sets and dictionaries that are based
on search trees.
Fair enough. Most of the times, you implement your real-life meaning of
comparison and equality to make good use of such features. Or you don't
care if there is no order, just the need for fast retrieval based on
criteria you don't care about. I am not familiar with the definition of
ADT, but "algebraic" seems to indicate there is some mathematical set of
base rules that needs to be met by those data types, right? You make
them algebraic by making sure they follow the rules of algebra. Once
that's ensured, everything else is just that: algebra.
Again: A Sequenceable Collection makes sure objects are kept in a
defined order. "Definition" here is either some kind of sorting (you use
or override equality and comparison) or the order of adding to the
collection, or something else. That is the job of a
SequenceableCollection. Nothing more, nothing less.
But please let's end this discussion, I will try not to write anything
more on the topic. I stated my opinion which you asked for. If you don't
agree, good. I don't consider myself intelligent enough to redefine
Smalltalk, but in this case I have the feeling your idea doesn't qualify
for the base libraries. You know that by now, we disagree. good.
Joachim
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