Re: OO's best feature survey results
From: Alfredo Novoa (alfredo_at_ncs.es)
Date: 10/31/03
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Date: 31 Oct 2003 03:15:28 -0800
topmind@technologist.com (Topmind) wrote in message news:<4e705869.0310301438.7a9681cd@posting.google.com>...
> > You always need the boolean type.
> >
> > if a = '1' then
> > ...
>
> That could simply be a short-cut for:
>
> if isEqual(a, '1') then ....
Again isEqual returns a boolean value.
> Again, assume that "+" is just a shortcut for an
> Add() function. For the sake of argument, assume
> that Add is not a built-in function.
>
> c = add(a, b)
>
> >
> > This language is still typed, but I would like to detect the error in
> > compilation time.
>
> What Add() or isEqual() does is up to the implementor(s).
Then you can not detect many errors at compile time.
I don't know anybody except you that would like to use a language like
that.
It is harder to use and error prone without any gain. It is a
regression to assembler.
> > > "Type"
> > > is something very temporial in this approach.
> >
> > No, types are immutable and eternal, but variables may hold values of
> > many types.
>
> Didn't Universe just say that types are, or are often situational?
> You two should get on the same page, or perhaps agree that
> "type" is a psychological viewpoint and not a universal
> truth.
Type is a math concept. Types are independent to time.
> > How do you solve this?
> >
> > if '10' > '9' then ...
>
> See above.
I have not seen the solution.
You can't know if I want to make a string or a numerical comparisson.
> "Types" are too artificial IMO for many things, perhaps most.
There is nothing wrong in being artificial.
> > > Besides, typing working on a small scale does not necessarily
> > > translate to a larger scale. Extrapolating "integer" ADT
> > > type concepts to business entities is a big leap.
> >
> > Business entities map very well to relation typed variables (AKA
> > tables).
>
> I don't know that entity == type. If so, why have a separate
> term "entity"?
entity == type is a great blunder. But it is a very common blunder in
the OO world.
BTW type is a formal term while entity is not.
> > Without types the relational model can not exist.
>
> I disagree. True, the "Oracle way" and its clones may involve typed
> columns, but I don't see anywhere where relational theory
> demands types anymore than a procedural language does.
Relational theory demands at least boolean types, tuple types and
relation types.
Without types you don't have tables, you only have mem cells.
> Why not call them constraints instead of types?
Among other things because constraints don't have operations.
How do you represent a table with a string?
> Constraints can be mixed and matched also so that
> they do not always form a clean tree. In otherwords,
> a "set of constraints".
Type hierarchies are not always trees.
> This is turning into a definition issue. I don't question
> that everything can be viewed as types IF one wants to,
The type concept is precise. In a programming language a type can be
viewed as a set of values and a set of operators that act over that
values.
Regards
Alfredo
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