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Re: [ddlm-group] Use of elides in strings

Dear Colelagues,

   There is a difference between what are useful utitlties to have in
an API in support of CIF2 and what is formally part of the base CIF2.
I am all in favor of utiltities to apply and unapply the various
uses for the reverse solidus -- one for cleaning up python-style
use, one to handle the IUCr special characters, one for line folding,
etc., but I don;t think that means we have to make one of those
particular uses formally part of the base CIF2.


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


On Fri, 20 Nov 2009, Joe Krahn wrote:

> Unlike others here, I feel that a proper text archive library should be
> able to take any string from the calling application, and return that
> exact same string when reading it back in. It is the job of the archive
> format to avoid delimiter problems. An applications should be able to
> store and retrieve strings without such worries, and interface to an SQL
> database the same is it would interface to CIF. All commonly used
> database libraries work this way. Why should CIF continue to take an
> archaic approach?
> I essentially agree with the design below, except that the library
> should handle insertion and removal of the reverse solidus for the
> limited cases where it is required.
> If it is the client application's responsibility to deal with reverse
> solidus escape sequences, then the description below doesn't make sense.
> In that case, the reverse solidus never has any special meaning to CIF2.
> Instead, CIF2 simply disallows certain character sequences. A client
> application can use whatever it wants to encode/decode the disallowed
> character sequences.
> The advantage of having well-defined escape sequences at the I/O library
> level is that updates to the format do not require updates to client
> applications. A CIF client application should be able to send a string
> to the CIF library, and not have to know in advance what CIF revision is
> in use, or whether the string is semicolong block quoted or triple
> quoted. By requiring the client to escape invalid sequences, the client
> will have to escape strings differently, i.e. triple quote is OK withing
> semi-colon quotes, and a leading semicolon is OK within triple quotes,
> but not the other way around.
> Joe Krahn
> Nick Spadaccini wrote:
>> (a) The contents of delimited strings are returned as raw, with the token
>> delimiters removed.
>> (b) Where a delimiter character is to be part of the string, that character
>> must be preceded by a reverse solidus when written out to the file. When
>> read, any reverse solidus preceding a terminating character is deleted.
>> (c) It is the responsibility of the writing and reading application to
>> insert and remove the reverse solidus preceding the terminating character.
>> (d) Otherwise the presence of a reverse solidus in the string has no
>> meaning.
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