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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.

   Regards,
    Herbert

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

                  +1-631-244-3035
                  yaya@dowling.edu
=====================================================

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:
>>
>> SUMMARISING.
>>
>> (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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