Re: [boost] [PQS] various views?

From: Andy Little (andy_at_[hidden])
Date: 2006-06-19 16:17:26

Hi Janek,

"Janek Kozicki" <janek_listy_at_[hidden]> wrote in message
news:20060618012314.6b5d8aee_at_absurd...
> Andy Little said:     (by the date of Fri, 16 Jun 2006 10:01:06 +0100)
>
>> Working this way then assuming a PQS type is a model of Quantity then things
>> should work. This would allow the Geometry library to be decoupled from PQS.
>
> yeah, decoupling is what we need :)
>
>> - Yes free quantity,
>
>> - Must be able to switch this in and out for performance reasons,
>>   greatly affects how PQS might be used.
>
>> - Need various views.
>
> Can you elaborate a bit about views? Is it Jesper's mechanism
> ( length x = 10 * meter(); )
> or maybe the ability to choose between using only SI base units, or all SI
> units including powers of 10, or physicists units (electronovolt, speed
> of light = 1) ?

I see the easy to use syntax:

boost::pqs::length::m

as a 'view' of the
boost::pqs::t1_quantity<abstract_quantity<...>,unit<...>,value_type>

Another view might be

my::length

where only base units are used.

I can think of other ways to present the raw t1_quantity too. One might be just
to present the quantities and units you need in one header.

As for other unit systems, there is so much work in simply completing the
library for the SI system that I have decided not to try to cover other unit
systems, nor make any guarantees that PQS will work for them. The priority is to
get what is there to an acceptable standard for Boost. PQS needs a lot of
work to get up to boost standards.

regards
Andy Little