[boost] [PQS] simplifying the type signature?

From: Andy Little (andy_at_[hidden])
Date: 2006-06-14 15:22:35

"Janek Kozicki" wrote
> Andy Little said:     (by the date of Tue, 13 Jun 2006 00:59:11 +0100)
>
>
>> t1_quantity type in PQS is overcomplicated. Two decisions complicated the 
>> design
>> of t1_quantity. The first was the requirement to distinguish dimensionally
>> equivalent quantities (torque and energy say).
>
> IMHO this distinguish is not that important. We only need units so that
> compiler will check if there is any mistake in the formulas...

I think the ability to distinguish quantity types is important for other 
purposes.

> Difference between torque and energy happens only during serialization
> (print N*m, or print J ?), so maybe instead of complicated
> abstract_quantity_id, there should be just some extra argument/setting
> that will talk with serialization functions?

Having thought about that I come to the conclusion that it is worthwhile to have 
the extra complexity in the t1_quantity/fixed_quantity. Having some form of 
output/serialisation for quantities is seemingly trivial, something like a toy 
feature, but it is very useful indeed for demonstrating and communicating what 
the type can do and for diagnosing what it is doing with minimal effort.  That 
may seem trivial but that type of feedback is very helpfull in the first stage 
of trying out a library to see what it can do. I can speculate that is part of 
the reason for the good level of interest in PQS, because it helps when 
providing short examples  in discussions like this. That simple functionality is 
underrated IMO.

regards
Andy Little