Re: Extended modal types

[dewar@gnat.com (Robert Dewar)]

"Robert I. Eachus" <rieachus@attbi.com> wrote in message news:<3CF2C6AF.60607@attbi.com>...
> Florian Weimer wrote:

> You are probably thinking of public-key encryption where the keys and 
> modulii are too big for ordinary modular types anyway.   I was thinking 
> of many algorithms that use modular arithmetic to introduce 
> non-linearity, for example multiplying two four-bit nibbles mod 17.  In 
> cases like this, the modulus is a static part of the algorithm 
> definition, and needs to be prime for invertability.

The fact that there are many algorithms which need a particular datatype
with some particular properties is NOT a reason for putting the type into
the language as a primitive type.

All these arguments about cryptography and hashing were made in the URG
meeting which rejected the generalization of unsigned wrap around types
to general non-binary modulus values overwhelmingly. I think the URG had
it right and Ada 95 has it wrong.

There are lots and lots of types that belong in the language long before
non-binary modular types (one that jumps to mind as clearly more important
is multiple precision integer arithmetic -- but I would not put that in
either :-)