Re: Imitation is the sincerest form of flattery

[Hyman Rosen <hyrosen@mail.com>]

Dmitry A. Kazakov wrote:
> First of all, there is no contract. I want the compiler be
 > aware that it is going to be an array and check if it is.

You have proxy classes that deal with all of this stuff.
Everything is typechecked.

> Secondly to make A[i]=X working you have to use a reference. Now, let I a 
> have a packed bit array. What would be a reference to a bit? You would need 
> to build a fat pointer class to fix this. The array has to represent an 
> image in the video buffer. It has to be damn FAST. And where are 
> multidimensional arrays in C++? And where are slices? Well, for them we 
> need another class, etc. And what if A is a hash table, sparse array. It 
> would be monstrous. And I want it on the stack!

It's not monstrous at all. First of all, as an Ada programmer,
you should not be complaining about having to write extra lines
of code to do what you want, as long as its all nice and readable.
Second of all, just because you need classes to handle all of this
doesn't prevent things from being on the stack, or from being fast.
Third of all, there is plenty of existing code to do this sort of
thing, in Boost and elsewhere.

Remembering some of our previous threads, I would caution you that
the proper way to implement all of this will eschew inheritance and
use templates heavily. If you try to do this using OO, then yes,
your code will be miserably slow.

> IMO. The idea of treating
>     A[i]=X;
> as
>     Assign (Index (A, i), X);
> is a wrong one.

Why? In particular, this technique is used very often in C++,
especially with expression templates. One has Index(A,i) just
return a proxy class which holds A and i, and implements the
Assign to take such a class. Inline expansion does the rest,
usually resulting in code that looks like an open-coded version.