Re: S-expression I/O in Ada

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 08/09/2010 06:48 AM, Robert A Duff wrote:
>
> Look at how unsigned types are used in C.  size_t is a good
> example.  It's used to count up the sizes of things.
> If I have 1000 objects of size 10_000_000, the total
> size is 1000*10_000_000 = 10_000_000_000.  If that
> calculation wraps around on a 32-bit machine, the
> answer is just plain wrong.  I'd rather get Constraint_Error.

It seems to me there are 2 orthogonal issues: signed or unsigned representation, 
and overflow checking on or off. In this case, we'd like an unsigned 
representation (because we don't need negative values but do need as large a 
range as possible) with overflow checking on (we almost always want overflow 
checking on).

If integer types had been approached this way, perhaps "wrap around" would only 
happen on the base type of types without overflow checking.

-- 
Jeff Carter
"Run away! Run away!"
Monty Python and the Holy Grail
58

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