Re: [boost] Interest in dimension/unit-checking library?

From: Paul A Bristow (pbristow_at_[hidden])
Date: 2005-10-26 03:45:51

| -----Original Message-----
| From: boost-bounces_at_[hidden] 
| [mailto:boost-bounces_at_[hidden]] On Behalf Of Simon Buchan
| Sent: 26 October 2005 00:28
| To: boost_at_[hidden]
| Subject: Re: [boost] Interest in dimension/unit-checking library?
| >...
| not to mention the ones *I* had yet to conceive ;-)
| 
| Don't forget the particle/quantam guys! Their units under-flow SI 
| doubles! (Or at least loose some serious accuracy)

| > I worry that the compile times and complexity will outstrip 
| both hardware
| > and compilers, but the only way to find out is to try it.  
| So I would
| > encourage Matt to continue his efforts in this direction.
| > 
| A lot of time could be saved with good header design, I assume, but 
| there really is no way around some overhead.  Maybe some sort of 
| explicit instatiation and static linking stategy (whether in user or 
| library) could help.

Some VERY fancy meta-coding is required but the compile time effect on
real-life projects  remains difficult to predict.

| > Paul
| > 
| > PS My gut instinct is to enforce explicit conversions - 
| mainly as a matter
| > of documenting intent, but I am just about persuaded that 
| implicit can be
| > OK, provided it is loseless.
| > If we can have a way of highlighting when implicit 
| conversion takes place,
| > that could make everyone happier.
| > 
| Implicit lossy conversions are the worst curse a library can 
| inflict on 
| the user, IMAO.  Lossless is better, but I am only comfortable with 
| promotions, I don't even like int to double very much (as it 
| loses the guarantee of integralness).
| So yes, explicit only.

We are talking about implicit conversions from feet to meters here - almost
certainly lossless. You need to read Matt's quite complicated arguments for
these.  
 
| Try putting the line "-- " just before this, it marks this as 
| a sig, so 
| it won't be quoted in a lot of agents (AFAIK):
| > Paul A Bristow
| > Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB
| > Phone and SMS text [phone], Mobile and SMS text +44 
| 7714 330204
| > mailto: pbristow_at_[hidden]  www.hetp.u-net.com

Does this please you better?

--
Paul A Bristow
Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB
Phone and SMS text [phone], Mobile and SMS text [phone]
mailto: pbristow_at_[hidden]  www.hetp.u-net.com