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Subject: Re: Counter-proposal for variable arrays
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Date: Wed, 08 Oct 2003 06:56:37 GMT
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Date: 2003-10-08T06:56:37+00:00
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Dmitry A. Kazakov wrote:
> Mmm I guess array is something that one can pass as a parameter. For
> example:
> void Erase (char X [20])
> {
>    memset (X, 0, sizeof (X)); // How many element will be set?
> }

For C compatibility, C++ arrays have the same decay-to-pointer
semantics in many circumstances. To prevent this, simply use a
reference:

void Erase (char (&X)[20]) { memset(X, 0, sizeof(X)); }

>>Yeah. So what? What exactly would the implementation of an array of
>>class-wide elements look like, anyway?
> 
> Children_And_Pop_Up_Array :
>    Container 
>    (  1..20, -- Constrain the bounds
>       From => Child_Window'Tag, -- Constrain the elements
>       To => Pop_Up_Window'Tag
>    );
> 
> The array contains 20 elements of types between Child_Window and
> Pop_Up_Window. Note that because all possible types are known, the
> upper bound of the element size is also known. So the array could be
> allocated as usual.

This seems like a pretty specialized usage to me, not particularly
worthy of dedicated language support. For one thing, classwide types
are there to support object-oriented programming, where you don't
know at the declaration point what types will be used.

For your purpose above, can't you just use an array of variant records
instead?