Re: Erratum?

From: Kenneth Whistler (kenw@sybase.com)
Date: Mon Jul 12 1999 - 19:48:38 EDT


Jonathan asked:

>
> I see CLOCKWISE INTEGRAL and 2 subsequent characters listed in the
> "mirrored" section of the Unicode Standard. I don't know a lot about
> right-to-left writing systems, and less about how mathematics is layed
> out within them, but isn't the notion of "clockwise" based on the
> direction of the sun, and so the same in all writing directions?
>
> Are these 3 characters there erroneously?

The answer is no, they are not their erroneously. For mirrored layout
of mathematical text, all of the integral signs would have to be reversed,
and that would include these 3 unusual contour integrals.

However, my expectation would be that the sense of the arrows would not
also be mirrored during the mirroring of the integral sign, in an
appropriate font design. So to mirror 2232, you would reverse the integral
sign part of the glyph, but leave the ring showing clockwise direction.
(I could be wrong -- I haven't actually seen these characters laid out
in math set right to left.)

>
> And if there are there correctly, shouldn't COMBINING (ANTI-)
> CLOCKWISE RING OVERLAY and COMBINING (ANTI-) CLOCKWISE ARROW ABOVE be
> present as well?

No. And note, besides, that none of the three contour integrals in question
is given a decomposition mapping in the standard. They are more of the
characters on the edge, where adding an explicit decomposition doesn't
really help, and instead would likely just complicate handling them.

>
> (Maybe it's just the "integral" part that should be mirrored: in
> that case, a note would clarify the intention.)

Agreed.

--Ken



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