Re: Re: Re: Re: quantity libraries

From: Kevlin Henney (kevlin_at_[hidden])
Date: 2001-08-31 04:20:17

>   From: "Steven Youngs" <steve_at_[hidden]>
>From: "Kevlin Henney" <kevlin_at_[hidden]>
>> My preference is for 3, but I would be interested to know if anyone is
>> working with an application that would benefit significantly from
>> supporting two different underlying representations in the same program
>> at the same time.
>
>In some applications (CAD & CAM come to mind as these are the problem area I
>develop in) it is common to have different parts of the same application
>working in different units. As an example, the US car giants often
>sub-contract work across the border to Canada. Historically, the US
>companies supplied English (inch) data to the Canadian companies who,
>typically, worked in metric (mm in this case). So we have an inch
>denominated input file read into the application which is displaying mm
>denominated units to the user. When the user completes their work the output
>is, once again, inch denominated. This is all within the same application.

Sorry, I should have been clearer, this is not quite what I meant:
moving between inches and millimetres is a relatively common
translation, but they are not orders apart in the magnitudes and
significant figures they address. This is already covered by having the
program compile using SI units as its base, and providing constants for
inches etc, and address presentation through locales or explicit
functions.

Specifically what I was after was whether anyone was mixing radically
different units that would suggest favouring two different underlying
representations, eg megaparsecs and femtometres, and what issues they
had encountered and resolved.

>As an aside: none of our UK customers uses inch (English) data any more and
>even Microsoft Windows defaults to metric when configured for English
>(United Kingdom) regional settings.

Glad to hear it :-) Those legacy units are a pain.

Kevlin
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