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Re: [ddlm-group] A modest addition to the DDLm spec. .

Dear Herbert

I wasnt aware that "comments ... are allowed in the middle of bracketed constructs".
Is this true?

This is a genuine question (its not readily apparent from the spec I've been referring to, but I do
seem to recall an earlier example that suggested this).

On the matter of the string concatenation issue, despite the fact that much of my last contribution was
light-hearted (in the spirit of celebrating the fact that the encoding issue might be nearing closure), my
opening sentiment was genuine, i.e. I can see a real use for such a mechanism. The major drawback
(apart from this whole thing being quite a major change compared with CIF1), is the further restriction on
the use of + in non-delimited strings. My immediate thoughts are that this doesn't respect the spirit of
compromise that led to the solution to the encoding issue, and would present a huge hurdle before even starting on
accepting the possibility of such a mechanism. I light-heartedly threw in a single underscore as an alternative just
because it was the first token that sprung to mind (i.e. a character in an isolated state that has no other meaning?),
but I haven't investigated this further at this stage and might well be 'talking rubbish'.

Anyway, I'd welcome some info on the use of comments in the bracketed constructs.



From: Herbert J. Bernstein <yaya@bernstein-plus-sons.com>
To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
Sent: Thursday, 30 September, 2010 18:23:02
Subject: Re: [ddlm-group] A modest addition to the DDLm spec. .

It reduces the incompatability with CIF1 introduced by the change
in string quoting syntax, allowing the resulting CIF2 CIFS to
be much closer to their CIF1 originals, fills that gap
created by not dealing with elides for lone folding in
a simpler way, and conforms to well-established pratice in
multiple programming languages.  C manages to deal with this
using the blank as the concatenation operator at the C preprocessor
level, so we should be able to handle it at the lexical level.

  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
        Idle Hour Blvd, Oakdale, NY, 11769


On Thu, 30 Sep 2010, Bollinger, John C wrote:

> On Thursday, September 30, 2010 8:59 AM, Herbert J. Bernstein wrote:
>> The following issue came up during the encodings group discussion, but
>> is more properly a DDLm issue.  In order to simplify algorithmic
>> conversion of existing CIF1 quoted strings to valid CIF2 strings,
>> I propose the addition of the python string concatenation operator, "+",
>> in CIF2 documents.  The main value of this addition is to permit a
>> simple algorithmic conversion of CIF1 strings with embedded quote
>> marks to CIF2 strings that end on the first occurrence of the initial
>> quote.  While the use of text fields will suffice in many cases,
>> for regular expressions it is clearer and simpler to just break the
>> string, insert the terminal quote mark, insert a "+" and then restart
>> the string with a different quote mark.
>> Formally the proposal is:
>> When a quoted string is given as a data value in a CIF2 document,
>> it may be presented as multiple quoted strings concatenated by the
>> "+" operator.  [...]
> Would this issue be addressed well enough by converting single-quoted
> strings to triple-quoted form?  I guess that wouldn't allow for breaking
> up regexes, so maybe it's addressed by the remark about text fields.
> I recognize that from time to time it is convenient to break up long,
> single-line values, but I'm not yet persuaded that that is sufficient
> justification for this feature.  Adopting it would add an incremental
> complication to CIF parsing, and would add another incompatibility with
> CIF1, so the benefit should offset those costs.
> If breaking up regexes in particular is the motivation for this
> suggestion, then could that objective adequately be met by having DDLm
> use a regex language that allows non-significant whitespace, as Perl's
> comments mode does?
> Regards,
> John
> --
> John C. Bollinger, Ph.D.
> Department of Structural Biology
> St. Jude Children's Research Hospital
> Email Disclaimer:  www.stjude.org/emaildisclaimer
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