[boost] Re: physical quantities (was: runtime unit-modifiable ...)

From: David B. Held (dheld_at_[hidden])
Date: 2004-01-09 05:16:55

"Russell Hind" <rhind_at_[hidden]> wrote in message
news:btj5mf$82n$1_at_sea.gmane.org...
> [...]
> I can see that this redundancy may be useful.  We deal sometimes
> with wavenumbers (cm-1) which is actually a frequency
> (i.e. 100cm-1 == 3THz).

Technically, it's not a frequency.  A frequency is an event per
second, which makes it s^-1.  The wavenumber is related to the
frequency via the propagation velocity of the wave.  Since you're
talking about EM radiation, the velocity is about 3e10 m/s:

3e12 s^-1 / 3e10 cm/s  == 1e2 cm^-1

> I would hope that we could specify these units so that they
> couldn't be converted to a length by inverting the value even
> though that would give units of cm.

In that case, I think you want a user-defined unit/dimension, as
Jan says.  A library which does not easily support user-defined
units would probably be missing a large segment of the user base,
no?

Dave

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