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New accent modifier types?

  • To: "Discussion list of the IUCr Committee for the Maintenance of the CIFStandard (COMCIFS)" <comcifs@iucr.org>
  • Subject: New accent modifier types?
  • From: Joe Krahn <krahn@niehs.nih.gov>
  • Date: Tue, 06 Mar 2007 12:55:58 -0500
When I first looked into accents, I thought the Latin1 and Latin2
character groups should be sufficient, but Latin3 and Latin4 are needed
to include some characters accents like over-bar. But, they also include
a few other unusual (to me) modifiers like Horn and Hook. It would not
be too hard to define modifiers for these. Would these be useful to
anyone, or are these excessive for the needs of CIF markup? Should we
ask somebody from Iceland?

What do people think about including a blank space as a modifiable
letter? The one caveat is "\% " as the degree sign instead of "\%".
Also, there could be a rule that a disallowed letter shows the accent as
a separate character, so "\%F" would be "<degree sign>F" and not F-ring,
because there is no F-ring.

What opinions are there on deprecating the bare letter codes -- the ones
with no leading backslash? Right now, they are all in the "accepted by
convention" list, so it seems to me that deprecating them is not so bad.
Is anybody in favor of keeping the bare mnemonics?

Also, the current set has single-bond graphically, and other bonds by
name. What do people think of using graphics in all cases, with
characters used in SMILES/SMARTs? This could have either one or two
backslashes:

\\--  single bond
\\==  double
\\##  triple
\\$$ or \\4- quadruple (Some SMARTS use $)
\\5-  quintuple (almost useless, but not impossible)

Joe Krahn

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