Re: [Boost-users] size_type doubts / integer library..

From: Michiel Helvensteijn (m.helvensteijn_at_[hidden])
Date: 2008-08-17 13:13:28

Zeljko Vrba wrote:

> Actually, I think I could simplify my requirements a bit:

I strongly agree with your proposal, and pretty much everything in your
post.

I would also like the possibility to explicitly state the lower- and
upper-bound in the type and the possibility to use a dynamic integer
(without any bounds), should the need arise.

In my opinion, the ideal solution would be to have only one int type in the
language, which would conceptually have no bounds. Convenient sub-types
(like uint) would be defined which would enforce type-invariants (like:
value >= 0). The programmer may also define his own sub-types. All
int-types would be compatible, however, and behave correctly in a
mathematical sense. If an operation between two integers overflows, an
assertion failure would arise.

This is clearly not possible for C++. But I'm designing a programming
language where integers work this way. The hope is that the bounds of a
plain int may be found (formally proved) at compile-time, so it can be
cleanly mapped to a hardware-int without any runtime overhead. If the
programmer specifies bounds, they are either proved correct at compile-time
or enforced at run-time. In all other cases, a dynamic int is used. This
should completely eliminate unexpected runtime overflow.

I'm also thinking of making int itself a subtype of a bit-array, which would
take care of bit-shift operations. But I'm not really sure how that would
work yet for all integers, since I would like to make the behavior hardware
independent and predictable.

-- 
Michiel Helvensteijn