Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ddlm-group] Characterset of non-delimited strings insidecompound data items

While I have no particular objection to excluding the close brackets from
non-delimited strings, personally I think making easy use of flex a
criterion for the design of CIF2 is not a good idea. -- 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 Tue, 9 Nov 2010, James Hester wrote:

> Dear DDLm group,
>
> John Bollinger has alerted me to a glitch in the current DDLm
> specification, to wit: (i) close bracket characters are allowed as
> non-final characters in a non-delimited string, and (ii) there is no
> requirement for whitespace between a datavalue and the close bracket
> symbol that denotes the end of a table or list value.
>
> This means that, in order to decide whether a close bracket character
> terminates a list or is just another character in the non-delimited
> string, the parser must look ahead, potentially many levels of
> nesting.  For example:
>
> _t            [outer [inner1 inner2]]
>
>
> The parser does not know that the first close bracket closes the inner
> list until it has read past the second close bracket.   Or even more
> confusingly:
>
> _t            [ depth_1 [ depth_2 [ depth_3 x=a1[a2[a3[a4[i]]]];]]]
>
>
> While this behaviour is not intractable, it is also not possible to
> use simple lexing tools (e.g. flex) to handle such syntax.  I would
> therefore like to propose the following change to the current draft
> specification:
>
> "The characters ']' and '}' may not appear anywhere in a non-delimited
> datavalue"
>
> James.
> -- 
> T +61 (02) 9717 9907
> F +61 (02) 9717 3145
> M +61 (04) 0249 4148
> _______________________________________________
> ddlm-group mailing list
> ddlm-group@iucr.org
> http://scripts.iucr.org/mailman/listinfo/ddlm-group
>
_______________________________________________
ddlm-group mailing list
ddlm-group@iucr.org
http://scripts.iucr.org/mailman/listinfo/ddlm-group

Reply to: [list | sender only]
International Union of Crystallography

Scientific Union Member of the International Council for Science (admitted 1947). Member of CODATA, the ICSU Committee on Data. Member of ICSTI, the International Council for Scientific and Technical Information. Partner with UNESCO, the United Nations Educational, Scientific and Cultural Organization in the International Year of Crystallography 2014.

ICSU Scientific Freedom Policy

The IUCr observes the basic policy of non-discrimination and affirms the right and freedom of scientists to associate in international scientific activity without regard to such factors as ethnic origin, religion, citizenship, language, political stance, gender, sex or age, in accordance with the Statutes of the International Council for Science.