[boost] Re: [rational] Announcing new maintainer -- call forfeature requests

From: Jonathan Turkanis (technews_at_[hidden])
Date: 2005-03-31 16:15:42

Andy Little wrote:
> "Jonathan Turkanis" <technews_at_[hidden]> wrote:

>> Would it be kosher for me to grab a bigint class from the Yahoo files
>> section --
>> say the one by  Ronald Garcia and Andrew Lumsdaine -- make sure it
>> is in good shape, and let it be the default template parameter to
>> rational?
>
> Surely int should be the default parameter (if any). Using bigint
> turns it from a relatively lightweight to a heavyweight type.

The reasons I would make it the default parameter are

- it's safer than a limited precision type
- I wouldn't have to give it a public name, though it could be accessed as
rational<>::int_type.

I don't think it would discourage users from using rational<int> where
appropriate.

> In many
> uses of rational
> the values are unlikely to overflow. Some uses are in dividing a
> circle into degrees, minutes, or seconds, power of dimension in a
> runtime physical-quantity, Storing imperial lengths eg 1 1/8 "
> (inch). I would guess that these are the major uses of rational and
> all have values in quite a small range.

Sounds like a good argument that rational is not completely useless without
rounding. Andras?

> And of course making bigint the default parameter introduces a
> dependency, which is at least untidy.

Good point.

> BTW why doesnt boost::rational have a 'value_type' member rather than
> the obscure 'int_type'?

You'd have to ask Paul. I would guess it's mean to reflect the requirements on
the template parameter.

> Further If the mpl rational (or fraction) becomes part of boost:
> http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?MPL_TODO_List.
>  it would be useful to allow interaction between the compile time and
> run time types:

I agree. But let's wait a bit.

Jonathan