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Re: [ddlm-group] Space as a list item separator

Dear all

I was chatting with the man who 'writes the cheques' yesterday about some of the
changes he might expect with CIF2, and based on this I feel I ought to at least have
a go at exploring a 'minimally disruptive' approach, so at the risk of being shouted at,
here goes at a slightly different way of looking at CIF:

CIF contains a list of strings separated by whitespace.

A string can be nondelimited or delimited.

Nondelimited strings have a restricted character set (minimally whitespace is excluded)

A nondelimited string cannot start with any of the delimiters (obviously)

Nondelimited strings can have special meaning governing what follows them:

    reserved words, e.g. loop_

    tags, e.g. data_ , _foo

    single-byte nondelimited strings, e.g. [ ] { } :

All other strings are treated as raw data values


There, least I can say I tried :-)

Cheers

Simon


From: SIMON WESTRIP <simonwestrip@btinternet.com>
To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
Sent: Saturday, 28 November, 2009 10:01:38
Subject: Re: [ddlm-group] Space as a list item separator

I had been under the assumption that the separation of list items by a comma was 'set in stone'
(and was one reason for dropping the CIF1 syntax of requiring space after data values),
but if its up for negotiation I would opt for using the space as a separator as elsewhere in the CIF,
partly because then a list can essentially be treated much like a single-item loop - i.e. same basic parsing
of <value><space><value><space>...

Cheers

Simon


From: Herbert J. Bernstein <yaya@bernstein-plus-sons.com>
To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
Cc: Nick.Spadaccini@uwa.edu.au
Sent: Friday, 27 November, 2009 11:43:10
Subject: Re: [ddlm-group] Space as a list item separator

Dear Colleagues,

  I have no objection to accepting either comma or whitespace
as a valid separator in a list.  I can't object -- I have been
coding to that standard since 1997, and now would only have to
remove the message generated for the case of the space.  We already
accept multiple glyphs as valid separators at all levels:

  whitespace itself it one of several character sequences in rather
complex combinations:  any number of blanks, tabs, newlines and comments.
The comma itself is handled in a complex way.  We accept (or should accept) any whitespace before and after a comma as valid, as in
{a,b} versus {a , b }.  Adding the option of leaving out the comma
itself and just having the whitespace as the separator make just
as much sense.

  I see nothing to be gained by now forbidding the comma.  The meaning of {a,,b,} is the same as {a,.,b,.} or {a,?,b,?} or, under this new (and I think more sensibsle and realistic approach) {a . b .} or {a ? b ?}.

  The blank reads particularly well in dealing with vectors and matrices. The comma reads well when dealing with strings.

  I think we would do best with both as valid alternatives (no error, no warning for either one).

  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, 27 Nov 2009, SIMON WESTRIP wrote:

> At first glance, you're considering using space instead of commas as list
> separators?
> which is not so far away from the CIF1 requirement of space following a
> delimiter?
>
> But I'm only on my first cup of coffee this morning :-)
>
> ____________________________________________________________________________
> From: Nick Spadaccini <nick@csse.uwa.edu.au>
> To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
> Sent: Friday, 27 November, 2009 7:46:44
> Subject: Re: [ddlm-group] Space as a list item separator
>
>
>
>
> On 27/11/09 2:32 PM, "James Hester" <jamesrhester@gmail.com> wrote:
>
> > See comments below:
> >
> > On Fri, Nov 27, 2009 at 3:09 PM, Nick Spadaccini <nick@csse.uwa.edu.au>
> wrote:
> >> Timely email, come in just after the one I sent.
> >>
> >> My position is if we specify the syntax then we encourage its correct use
> but
> >> acknowledge that there may be cases where one might be able to recover
> >> intent. But I wouldn?t encourage those cases.
> >
> > Absolutely, which is why I would like to elevate space-separated list
> items to
> > be correct syntax rather than 'wrong but intent is clear' syntax.
> >>
> >> You could say that token separator in lists are a or b or c, but that
> just
> >> adds a level of complexity for very little gain. The choice of comma
> makes it
> >> seamless to translate from the raw CIF data straight in to most language
> >> specific data declaration. The only language I know that accepts one or
> the
> >> other or both is MatLab.
> >
> > Re ease of translation: you speak as if a viable approach to a CIF data
> file
> > is to take whole text chunks and throw them at some language interpreter,
> > without doing your own parse.  Quite apart from being a rather unlikely
> > approach, this is impossible, as without parsing you won't know where the
> list
> > finishes.  If you do do your own parse, you can populate your
> datastructures
> > directly during the parse, and what list separator was originally used in
> the
> > data file is completely irrelevant.
> >
> > Re complexity: not sure how you are planning to deal with whitespace in
> the
> > formal grammar, but consider the following, where I have assumed that each
> > token 'eats up' the following whitespace.
> >
> > <dataitem> = <dataname><whitespace>+<datavalue>
> > <datavalue> = {<list>|<string>}<whitespace>+
> > <listdatavalue> = {<list>|<string>}<whitespace>*
> > <list> = '[' <whitespace>* {<listdatavalue>
> > {<comma><whitespace>*<listdatavalue>}*}* ']'
> >
> > If we make comma or whitespace possible separators, the last production
> > becomes:
> > <list> =  '[' <whitespace>* {<listdatavalue> {<comma or
> > whitespace><listdatavalue>}*}* ']'
> >
> > This looks like no extra complexity, and from a user's point of view
> > whitespace as an alternative separator is simple to understand and
> consistent
> > with space as a token separator used everywhere else in CIF.  Anyway, if
> > reduction of grammar complexity is your goal, you can just completely
> exclude
> > commas as list separators!
>
> Why not? Make them spaces only, and you become consistent across the board.
> I have to think about the possibility of pathological cases where spaces
> won't work. I can't think of any at the moment.
>
> >
> > Some questions about how commas behave:
> > 1: is a trailing comma e.g. [1,2,3,4,] a syntax error?
> > 2. are two commas in a row a syntax error? E.g. [1,2,3,,4]
>
> I would say yes to syntax error. I an easily determine they may need to be
> an additional list value, but can't determine what.
>
> > Note the above productions assume that the answer to both is yes.
> >
> >>
> >> What big advantage to a language is there to specify you can use a comma
> or
> >> whitespace as a token separator? Will you be happy with the first person
> who
> >> interprets this as being ok
> >>
> >> loop_
> >>   _severalvalues 1,2,3,4,5,6,7 # these being the 7 values of
> severalvalues
> >>
> > Note sure what you are getting at here: I am proposing the following:
> >
> > _nicelist      [1 2 3 4 5 6 7]
> >
> > being the same as
> >
> > _nicelist      [1,2,3,4,5,6,7]
> >
> >  Don't see how this relates to loops.
>
> The point was, once you say a space and comma are equivalent token
> separators then will it be an interpretation that they are always so even in
> loops? My example was not a list, just 7 values that were separated by
> commas not spaces.
>
> >
> > James.
> > ------
> >>
> >> On 27/11/09 11:41 AM, "James Hester" <jamesrhester@gmail.com
> >> <http://jamesrhester@gmail.com> > wrote:
> >>
> >>> Dear All: looking over the list I posted previously of items left to
> >>> resolve, I see only one serious one outstanding: whether or not to allow
> >>> space as a separator between list items.  Nick has stated:
> >>>
> >>> " I will propose it has to be a comma, but make the coercion rule that
> space
> >>> separated values in a list-type object be coerced into comma separated
> >>> values. That is, read spaces as you want, but don't encourage them."
> >>>
> >>> I would like to counter-propose, as Joe did originally, that whitespace
> be
> >>> elevated to equal status with comma as a valid list separator.  I see no
> >>> downside to this.  Would anyone else like to speak to this issue before
> we
> >>> vote?  In particular, I would be interested to hear why Nick doesn't
> want to
> >>> encourage spaces.
> >>
> >> cheers
> >>
> >> Nick
> >>
> >> --------------------------------
> >> Associate Professor N. Spadaccini, PhD
> >> School of Computer Science & Software Engineering
> >>
> >> The University of Western Australia    t: +61 (0)8 6488 3452
> >> 35 Stirling Highway                    f: +61 (0)8 6488 1089
> >> CRAWLEY, Perth,  WA  6009 AUSTRALIA   w3: www.csse.uwa.edu.au/~nick
> >> <http://www.csse.uwa.edu.au/%7Enick>
> >> MBDP  M002
> >>
> >> CRICOS Provider Code: 00126G
> >>
> >> e: Nick.Spadaccini@uwa.edu.au <http://Nick.Spadaccini@uwa.edu.au>
> >>
> >>
> >>
> >> _______________________________________________
> >> ddlm-group mailing list
> >> ddlm-group@iucr.org
> >> http://scripts.iucr.org/mailman/listinfo/ddlm-group
> >>
> >
> >
>
> cheers
>
> Nick
>
> --------------------------------
> Associate Professor N. Spadaccini, PhD
> School of Computer Science & Software Engineering
>
> The University of Western Australia    t: +61 (0)8 6488 3452
> 35 Stirling Highway                    f: +61 (0)8 6488 1089
> CRAWLEY, Perth,  WA  6009 AUSTRALIA  w3: www.csse.uwa.edu.au/~nick
> MBDP  M002
>
> CRICOS Provider Code: 00126G
>
> e: Nick.Spadaccini@uwa.edu.au
>
>
>
>
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