Re: Seeking for papers about tagged types vs access to subprograms

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Tue, 07 May 2013 22:27:58 +0200, Jacob Sparre Andersen news  
<randy@rrsoftware.com> a écrit:

> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:1luaso698dpcc$.rrv8385qwl92.dlg@40tude.net...
>>> On Mon, 6 May 2013 20:09:46 -0500, Randy Brukardt wrote:
>>>
>>>> The idea of indexing a numeric type is silly,
>>>
>>> Not at all, consider Unit type declared modular because it has to be  
>>> used
>>> as a discriminant. At the same time Unit is a composite of powers for
>>> mass,
>>> time, current, temperature etc. One would like to have it indexed  
>>> (viewed
>>> as an array or as a record).
>
> It might make sense to view it as a record (a capability not in Ada  
> 2012),
> but it makes little sense to view it as an array (a list of identical
> components indexed by a potentially *computed* index). There are a lot of
> abuses of arrays out there that would be much better written as records.

Look at the deflate specification (RFC 1951), this makes sense with it to  
see modular types as an array of bits. Anyway, user‑defined indexing is  
supposed to be a client‑side interface to some data type, most likely and  
allowed to be opaque, so what makes the less sense, is assertions about  
what the underlying type should be.

-- 
“Syntactic sugar causes cancer of the semi-colons.” [1]
“Structured Programming supports the law of the excluded muddle.” [1]
[1]: Epigrams on Programming — Alan J. — P. Yale University