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Re: [ddlm-group] Focusing the elide discussion

Just realized that scheme A does not require the quote to be elided unless it is followed by the triple-quote - so my objection
should be that it does not address line folding.

As I understand it, there are a couple of fundamental difference between the schemes that allows them to be split into two classes:

1) those which operate on the string once the lexer has identified it (C, D, E, F, F')

and

2) those which require the lexer to process the escape sequences in order to identify the string (P, A, B)

So, schemes of class 1) are not really an ideal stepping stone towards schemes
of class 2)?

Each class of scheme has its merits - I'm still weighing these up, in particular remembering that CIF is based on
a fairly simple tagging system.

Anyway, just some more thoughts to clutter up the forum :-)

Simon

From: SIMON WESTRIP <simonwestrip@btinternet.com>
To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
Sent: Wednesday, 12 January, 2011 15:40:12
Subject: Re: [ddlm-group] Focusing the elide discussion

Best: F or F' (havent decided which I prefer at this stage)

Bearable: with 'one sentence' reason for not favouring:

E  -  as CIF2 supports unicode, a mechanism to represent unicode using ASCII should be applicable to any CIF value that allows text, however it is delimited.

C, D  -  post-elides are not a 'familiar' concept

A  -  only really addresses one issue, \"""", while introducing the need to use \\" to represent \", which is familiar to e.g. TeX users and IUCr authors

B  -  as for E

At a pinch:

P  -  I need more than one sentence to explain why I dont favour this, but in summary: it requires a completely different set of rules compared with the rest of CIF

None of the options is unworkable, but considering what is actually needed to address the issue of being able to represent
any string within CIF, and to a lesser extent the issue that CIF2 specifies a line-length limit but doesnt provide a line folding protocol,
I'd rather keep things as simple as possible (especially for those CIF users who work with the raw CIF).

Cheers

Simon


From: James Hester <jamesrhester@gmail.com>
To: ddlm-group <ddlm-group@iucr.org>
Sent: Wednesday, 12 January, 2011 13:20:09
Subject: [ddlm-group] Focusing the elide discussion

By my count there are 6 distinct proposals for eliding triple-quoted
strings on the table, which I have listed below.  In order to get an
idea of where we all stand and which proposals are most likely to
succeed, I'd like to invite you all to reply to this email with a list
of proposals which you would find acceptable.  If you like, you can
rank them in order of preference.  In the list below I've given short
descriptions, but you should refer to the original emails for the full
details.  The opinions of COMCIFS voting members are of course most
significant at this juncture, but I for one am interested in the
thoughts of the other members as well.

Proposal P (for Python): Ralf's original proposal to do everything as in Python
Proposal A: <backslash><delimiter> elides the delimiter, no other
sequences are significant
Proposal B: \uxxxx to represent Unicode characters, no other sequences
are significant
Proposal C: as yet unspecified character post-elides the delimiter
where necessary
Proposal D: as for C, except post-elide character is given immediately
before opening triple delimiter
Proposal E: (John B's suggestion) \uxxxx for Unicode character
together with \<newline> and \\
Proposal F: (Simon's proposal) \<newline> and \\ only
Proposal F': (My slight tweak of Simon's proposal) \<newline> only
when not preceded by \

I find proposal P unacceptable, and would rank the others in order of
preference roughly as follows:

Best: F', F, C
Bearable: A, B, E
In a pinch: D

--
T +61 (02) 9717 9907
F +61 (02) 9717 3145
M +61 (04) 0249 4148
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