Re: Class objects work like built-in types, but is it worth it?

From:
=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 28 Oct 2008 18:55:42 GMT
Message-ID:
<OeJNk.3628$U5.23898@newsb.telia.net>
On 2008-10-28 16:00, tonytech08 wrote:

On Oct 26, 2:49 pm, Erik Wikstr??m <Erik-wikst...@telia.com> wrote:

On 2008-10-26 05:07, tonytech08 wrote:

On Oct 24, 4:25 pm, Juha Nieminen <nos...@thanks.invalid> wrote:

tonytech08 wrote:

On Oct 23, 5:42 pm, Juha Nieminen <nos...@thanks.invalid> wrote:

tonytech08 wrote:

How valuable is it that class objects behave like built-in types?


  Without this feature there would be only two possible choices:

1) Generic containers cannot support built-in types, only user-defined
classes.


The way STL containers are designed is not the only possibility. You
seem to be fixated on STL container designs/architecture. (?)


  Well, tell me how you would implement a generic data container which
efficiently supports both built-in types and user-defined classes.


Why is that important?


Because we use use such containers every day and have found them really
useful.


It may be mildly convenient, but hardly necessary or even important.


Says you, allow me to disagree.

(like they are in
some languages). While in some cases this would be a useful thing (which
is the reason why those some languages do it in the first place), this
would seriously hinder the efficiency of built-in types.


It wouldn't change built-in efficiency in the least or in any way.


  Exactly how would you create a generic data container which supports
both built-in types in the most efficient way possible *and*
user-defined classes if, as you suggest, the latter do not behave like
built-in types?


Why is that important?


Consistency is very important when writing software, we do not need the
additional complexity of having different containers for different
types.


Pushing complexity to another area is just pushing it around rather
than finding an elegant solution. And yes, sometimes the elegant
solution has some amount of compromise to avoid that complexity. If
one is real anal about it, well, C++ the language may be what you end
up with? "Refactoring" the language may be in order (on alternative).


To me it seems like we pushed the complexity all the way out of existence.

If you need to different containers (one for built-in types and
one for others) it means you need two sets of code, which meant you
double the amount of bugs, double the maintenance const, double the
things to keep track of, etc.


So, how many linked lists of integer values have you used in code? It
appears that not supporting built-in types for some containers would
encourage better programming practice (going by just that one
example).


Linked lists? None in any non-trivial program, but I've used vectors
(lots of them), heaps, stacks, and queues with integers.

Did
you mean using those things from containers? Perhaps you are thinking
built-in arrays and not containers at all?


  Built-in arrays *are* containers. The only difference is that they are
not dynamic, but that's irrelevant.


Ah, the "built-in type" arrays ARE containers. Well if you have a
paradigm about what a container is, then all thing will look like a
nail I guess.


Again the messed up proverbs. Yes, we have a definition of what a
container is. In short it is something which can contain one or more
other things and there are ways of accessing these things. Such as an array.


Array is a tricky one because there are built-in arrays which are
fundamentally different from a array "container". So to not muddle the
discussion with "corner cases", a different container abstraction,
such as linked list, would probably be better to use as an example.


Sorry, but no. I use neither array or linked list as the definition of
what a container is, I think that both arrays and lists (as used in
functional languages) are containers.

I think I've noted before or above that if you start with the thought
that "a built-in array is a container", a perverted definition of
"container" will result. A built-in array is a type rather than a
container (by "my" definition of container anyway).


Actually if we say that an array is a container we say that it fulfils
the requirements of a container, not the the requirements of a container
is to be like an array. Or in OO terms: an array implements the
interface container, but there might be many other implementations of
the same interface.

--
Erik Wikstr??m

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