Re: [boost] New Boost.XInt Library, request preliminary review

Subject: Re: [boost] New Boost.XInt Library, request preliminary review
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-03-30 07:13:02

Chad Nelson wrote:
> Someone-else-whose-name-was-elided wrote:
>
> > invmod and random_prime?  These hardly seem like
> > fundamental operations that necessitate this "invasion" into an
> > otherwise pure big-integer interface ;)
>
> I have to disagree, only because one of the main reasons
> people want to
> use a large-integer library is for cryptography, and those
> two functions *are* fundamental to that.

"One of the main reasons," not "the only" reason.  Hence, cryptography functionality, which surely is more than those two functions, should be in a separate library.

> > Returning optional values is precisely the raison d'etre of
> > Boost.Optional, and you're ending up just building its functionality
> > directly into the xint::integer class, so instead of xint::integer,
> > we really have a boost::optional< xint::integer >.  I don't
> > like that
> > :/  What did you find about Boost.Optional that was difficult for
> > users to understand?
>
> That it acts like a pointer but isn't one. Less experienced developers
> often find even pointer syntax hard to master, and unfortunately, they
> are the majority of programmers. I was trying to make it as easy as
> possible for anyone, no matter what their level of experience, to use.

This is being proposed as a Boost library.  We can assume enough knowledge to use Boost.Optional, which isn't great.

> > The interface to invmod and random_prime should be built around the
> > interface of xint::integer, not the other way around.
>
> Sorry, not good enough. They're an important part of the
> interface, and their requirements affect it too.

That's not a sufficient reason for their inclusion in a big integer library.  Rather, the big integer library needs to be designed well to support those functions and many others.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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