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From: Paul A. Bristow (boost_at_[hidden])
Date: 2004-01-09 07:30:37

Should you being carrying out computations with mils (and perhaps mm) as
_integers_, rather than as any sort of real?

Just to muddy the water further ;-)


Paul A Bristow, Prizet Farmhouse, Kendal, Cumbria, LA8 8AB UK
+44 1539 561830 Mobile +44 7714 33 02 04

| -----Original Message-----
| From: boost-bounces_at_[hidden]
| [mailto:boost-bounces_at_[hidden]]On Behalf Of Dan W.
| Sent: Friday, January 09, 2004 6:40 AM
| To: boost_at_[hidden]
| Subject: [boost] Re: physical-quantities
| And I've got another argument for why each unit type should represent
| itself as one:
| Back to the circuit layout CAD problem, combining millimeters and mils:
| If the library were to force conversions to one or the other, it would
| incurr cumulative errors in the non-default units system. I.e.: If we
| select millimeters as the default, and I have a long connector whose
| pins are spaced 50 mils apart, if I accumulate 50 mils many times, and
| each time it is converted to millimeters and then added to an
| accumulator, the error in each conversion is cumulative. If I select
| mils as the default, and I have another long connector on the other side
| of the board, and its pins are spaced 1.5 mm apart, same thing will
| happen: conversion to mils each time (which is also inefficient, BTW),
| and the error in each conversion is cumulative.

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