RE: [boost] Physical quantities (was Re: Yet Another Units Library)

From: Paul A. Bristow (boost_at_[hidden])
Date: 2003-10-27 06:05:05

-----Original Message-----
From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]]On
Behalf Of Matthias Schabel
Sent: Sunday, October 26, 2003 5:17 PM
To: boost_at_[hidden]
Subject: [boost] Physical quantities (was Re: Yet Another Units Library)

| A couple of other issues that have arisen :
<snip>
|
|A Second, if all internal calculations are forced to long double, we are
|forcing more precision than may be necessary or desired and at the same time
|preventing the
|use of class value_types which have higher precision (like a quad precision
|double or BCD value).

It would certainly be a pity if a solution precluded user-defined precisions
(higher like NTL 128 bit quad_float and perhaps lower for those embedding in
toasters).  It would be even more of a pity if user defined types which included
uncertainty estimates were excluded.

|2) comparison operators also may have problems with unit conversions due to
|numeric precision issues.
|It is probably best to prohibit implicit unit conversions for this reason as
well.

Agreed.

|As a further demonstration, I've written a quick-n-dirty Measurement class
which |encapsulates both
|values and errors, along with standard error propagation for basic arithmetic
|operations. Its use
|in conjunction with the units library is shown in mcs_units_2.zip in the files
|section on yahoo.

Thanks will read.

Paul

Paul A Bristow, Prizet Farmhouse, Kendal, Cumbria, LA8 8AB  UK
[phone]   Mobile [phone]
mailto:pbristow_at_[hidden]

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