Re: OO, C++, and something much better!

[jsa@alexandria (Jon S Anthony)]

In article <yf3ybclbavi.fsf@sabi.demon.co.uk> piercarl@sabi.demon.co.uk (Piercarlo Grandi) writes:

> jsa> I think what you really want to say is simply that you don't think
> jsa> the standard mathematical usage is appropriate in the context of PL
> jsa> definitions.
> 
> Not at all: I don't think that the use of the word "operator" as a short
> form of "operator function" is what people mean by "operator" on its own.

What people?  Where's the evidence?  Certainly in mathematics it is
_common_ practice to use the word "operator" as short for "operation"
(aka, your "operator function").


> There in maths operator symbols that do not label operator functions;
> viceversa there are operator functions that are not labeled by an
> operator symbol.

So what?  You are all hung up on syntax and glyphs.  Glyphs _can_ be
important - no doubt about it.  But that importance does not extend to
the _definition_ of the concept involved.


> I am discussing what makes a symbol into an operator symbol
> (distinguished syntax and usually lexicon); Alan when a procedure
> should be called an "operator", even if is name does not at all look
> like an operator.

So?  None of this conflicts with what I said: you don't want to use
the standard mathematical definition in PL/CS land.  Fine.  And
mathematicians don't want to use your goofy definition based on syntax
and glyphs.


> In my view 'sizeof' is an operator; he seems to be arguing that
> 
>   (lambda (x y) (+ (^ y 3) (+ 2 (* y (* e y)))))
> 
> is an operator because it computes an operator function.

I can't speak for him, but I don't think you have this even close to
right.  No one is talking about functors.


> jsa> That's only because you've become attached to this idea that
> jsa> operators and operations are some how defined by their "looks".
> 
> Well, of course, because we are discussing operaror _symbols_, not
> functions or procedures. The discussion arose out of discussing "+", if
> I remember well.

What do you mean "of course"??  And of course we are discussing _both_
because if we weren't there would be nothing to say.


> jsa> Not so.  If anything, it is the other way around.  The semantics
> jsa> come first and if it is deemed "special enough" to call out in a
> jsa> certain context, a particular distinctive symbol (and much more
> jsa> rarely, syntax) is chosen.
> 
> But no! As you argue a few lines below, mathematicians use special

But yes.  That is exactly how it happens in mathematics.

> syntax and lexicon to label functions that are not operator functions!;

Sure.  So what?


> piercarl> examples and draw general rules. In maths operators are
> piercarl> symbols that essentially always have some distinguished
> piercarl> syntatic role, and very often are drawn from some
> piercarl> distinguished lexicon too.
> 
> jsa> Sorry, this is just is not true.  The following are operators on
> jsa> the set of Reals and none have any "distinguished syntax".
> 
> jsa> f(x) = x^2 + pi*x^(1/3)
> jsa> g(y) = y^3 + 2y*e^y
> 
> No, these are two _functions_ that belong to the set of _operator
> functions_.

What do you mean, "no"?  How is your characterization different than
saying they are operations, i.e., functions which are operators?  Or
are you complaining about the fact that I used the term "operator" to
refer to the operation (and not the glyphs)?  In this particular
context that would really be too much.


> piercarl> I am not quite sure that syntactic/lexical shorthands actually
> piercarl> help in programming, but most programming language designers,
> piercarl> in the doubt, provide some sort of maths-like distinguished
> piercarl> syntax for operators.
> 
> jsa> it isn't obvious that this helps a lot in programming.
> 
> Indeed! That is *my* point. In fact I think it is unhelpful. But then

Fine.  IMO, this is not very interesting.


> there is an opinion that programs, in particular OO programs, ``model
> directly the real world'', where the ``real world'' can be maths; and

So?  Depending on what you mean by "model" this might be true or it
might be simply confused.  Certainly OO people are more confused than
not.  But I don't think that has a lot to do with the glyphs being
used and the syntax for combining them.


> However I don't subscribe to that point of view; to me using
> notation to suggest that 'class complex' and 'the Complex plane' are
> in close correspondence is not such a good idea, and not very useful
> in any case.

The notation has nothing to do with it.  That problem is a semantic
problem - not a syntax problem.  People can (and do) confuse a concept
of a thing for the thing, confuse a word with its meaning, etc., etc.
None of this has to do with syntax and glyphs.

/Jon

-- 
Jon Anthony
Organon Motives, Inc.
Belmont, MA 02178
617.484.3383
jsa@organon.com