Re: Lower bounds of Strings

["Randy Brukardt" <randy@rrsoftware.com>]

IMHO, "String" shouldn't be an array at all. In a UTF-8 world, it makes 
little sense to index into a string - it would be expensive to do it based 
on characters (since they vary in size), and dangerous to do it based on 
octets (since you could get part of a character).

The only real solution is to never use String in the first place. A number 
of people are building UTF-8 abstractions to replace String, and I expect 
those to become common in the coming years.

Indeed, (as I've mentioned before) I would go further and abandon arrays 
altogether -- containers cover the same ground (or could easily) -- the vast 
complication of operators popping up much after type declarations, 
assignable slices, and supernull arrays all waste resources and cause 
oddities and dangers. It's a waste of time to fix arrays in Ada -- just 
don't use them.

                                                        Randy.



"Stephen Davies" <joviangm@gmail.com> wrote in message 
news:1cc09f04-98f2-4ef3-ac84-9a9ca5aa3fd5n@googlegroups.com...
>
> I'm sure this must have been discussed before, but the issue doesn't
> seem to have been resolved and I think it makes Ada code look ugly and
> frankly reflects poorly on the language.
>
> I'm referring to the fact that any subprogram with a String
> parameter, e.g. Expiration_Date, has to use something like
> Expiration_Date (Expiration_Date'First .. Expiration_Date'First + 1)
> to refer to the first two characters rather than simply saying
> Expiration_Date (1..2).
>
> Not only is it ugly, but it's potentially dangerous if code uses the
> latter and works for ages until one day somebody passes a slice instead
> of a string starting at 1 (yes, compilers might generate warnings,
> but that doesn't negate the issue, imho).
>
> There must be many possible solutions, without breaking compatibility
> for those very rare occasions where code actually makes use of the
> lower bound of a string.
>
> e.g. Perhaps the following could be made legal and added to Standard:
>
> subtype Mono_String is String (1 .. <>);
>
> One question with this would be whether or not to allow procedure bodies
> to specify parameters as Mono_String when the corresponding procedure
> declaration uses String.