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Re: [ddlm-group] CIF-2 changes

As I said in my previous email. The gain is that you can determine where you
are at a lexical level without having to go further in to the parsing. There
is a reason why languages use [] and {} separately, and that ease.

If computer scientists have learnt one thing in the last 50 years, it is how
to design and specify languages so that you avoid ambiguity and complexity.


On 30/10/09 10:53 AM, "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>
wrote:

> The question is one of what we gain from having both [] and {}.  I think
> Nick is right to consolidate them. -- 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 Thu, 29 Oct 2009, Joe Krahn wrote:
> 
>> I agree with James here. I don't see how brackets interfere with parsing
>> at all. A list bracket can only be misinterpreted if it follows a data
>> name with no intervening space, but that should be invalid anyhow,
>> right? Switching to parenthesis is reasonable, but it should not be done
>> just because brackets are part of the new STAR/CIF syntax.
>> 
>> As for the list examples below, why use commas instead of just quoting
>> and whitespace delimiters, as in the current STAR syntax? If commas are
>> used, commas would become a reserved character and need quoting or escaping.
>> 
>> I don't have strong opinions either way. My main interest is just to aim
>> for a well-defined syntax without any parsing ambiguities.
>> 
>> Joe
>> 
>> James Hester wrote:
>>> As the syntax that we have been developing now stands, the only reason
>>> for not using square brackets is so that it will be possible to
>>> correctly parse a CIF in which a space is accidentally missing between
>>> a dataname and a bracketed list.  This seems to me to be a pretty
>>> minor reason to fiddle with the bracket syntax, but having got that
>>> off my chest I don't have any objections to the revised syntax.
>>> 
>>> NB I believe Nick would like to drop the concept of tuples in DDLm and
>>> dREL altogether, with which I also agree.
>>> 
>>> On Thu, Oct 29, 2009 at 10:31 PM, Herbert J. Bernstein
>>> <yaya@bernstein-plus-sons.com> wrote:
>>>> I have no objection to Nick's approach.  I would suggest a straw vote as
>>>> soon as possible, so that we can have move forward on coding.  So to be as
>>>> specific as possible, here is what I think Nick is proposing:
>>>> 
>>>>   1.  All the bracketed constructs in a CIF be delimited by {}:
>>>>        Lists:  { ..., ... }
>>>>        Tuples: { ..., ... }
>>>>        Arrays: { ..., ... }
>>>>        Tables: { key:value, key:value } with the distinctions among them
>>>> made primarily by the type specifications. Note that the key in a table
>>>> should be a quoted string.
>>>> 
>>>>   2.  That array dimensions in a CIF also be delimited by {} as in
>>>> {3} or {3,4}
>>>> 
>>>>   3.  That the same changes be made in dREL
>>>> 
>>>> (Nick, did I get that right?)
>>>> 
>>>> I can work with all of the above, and I suspect Nick is right about the
>>>> long-term value of consistency here, and reasonably strong typing does
>>>> tend to reduce coding errors.  What do other people think?
>>>> 
>>>> 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 Wed, 28 Oct 2009, Nick Spadaccini wrote:
>>>> 
>>>>> The move away from [] lists to {} lists (thus overlapping with {}
>>>>> associative arrays) had to do with cleaning up the syntax under CIF-2.
>>>>> 
>>>>> There are legacy issues with existing CIF data names with embedded []
>>>>> which
>>>>> meant that using [ to initiate a list would come unstuck.
>>>>> 
>>>>> Accordingly to simplify matters and to move forward, I proposed using {}
>>>>> to
>>>>> define lists or associative arrays. The complication to the parser is that
>>>>> you must start to look inside the object to determine which it is.
>>>>> 
>>>>> That is CIF. dREL is a different matter but consistency is a good thing,
>>>>> so
>>>>> that it makes sense to keep the syntax the same as a CIF data file. Hence
>>>>> your transcription of the dREL code is correct. It makes my work a lot
>>>>> more
>>>>> difficult of course because until now I just called up a Python parser to
>>>>> handle almost all of dREL.
>>>>> 
>>>>> Such is life.
>>>>> 
>>>>> 
>>>>> On 25/10/09 10:24 PM, "Herbert J. Bernstein"
>>>>> <yaya@bernstein-plus-sons.com>
>>>>> wrote:
>>>>> 
>>>>>> Dear Colleagues,
>>>>>> 
>>>>>>    Please take a look at the dictionaries I have drafted at
>>>>>> 
>>>>>>    http://vcif.sf.net/cif2_dicts
>>>>>> 
>>>>>> and tell me if I am on the right track in trying to convert to CIF-2
>>>>>> format dictionaries.  I have taken all the August 2008 () style tuples in
>>>>>> the upper level and converted them to October 2009 CIF-2 {} style lists.
>>>>>> I have not changed any array dimension specifications, e.g. [*], nor the
>>>>>> innards of any methods.
>>>>>> 
>>>>>>    Questions:
>>>>>> 
>>>>>>    1.  Should the dimensions be changed, e.g. from [3] to {3}?
>>>>>>    2.  Should there be any changes in dREL methods themselves?
>>>>>> 
>>>>>> For example consider:
>>>>>> 
>>>>>> ======
>>>>>> save_function.SymEquiv
>>>>>>      _definition.id              'function.SymEquiv'
>>>>>>      _definition.update           2007-10-11
>>>>>>      _description.text
>>>>>> ;
>>>>>>       The function
>>>>>>                       xyz' =  SymEquiv( symop, symcat, xyz )
>>>>>> 
>>>>>>       returns a fractional coordinate vector xyz' which is input vector
>>>>>>       xyz transformed by the input symop 'n_pqr' applied to the symmetry
>>>>>>       equivalent matrix extracted from the category symcat.
>>>>>> ;
>>>>>>      _name.category_id            function
>>>>>>      _name.object_id              SymEquiv
>>>>>>      _type.purpose                Assigned
>>>>>>      _type.container              Array
>>>>>>      _type.contents               Real
>>>>>>      _type.dimension              [3]
>>>>>>       loop_
>>>>>>      _method.purpose
>>>>>>      _method.expression
>>>>>>       Evaluation
>>>>>> ;
>>>>>>       Function SymEquiv( c :[Single, Symop],    # symop string n_pqr
>>>>>>                          l :[Category, Tag],    # loop of symmetry
>>>>>> matrices
>>>>>>                          x :[Array, Real]    )  # fract coordinate vector
>>>>>>       {
>>>>>>               s = l [ SymKey( c ) ]
>>>>>> 
>>>>>>               SymEquiv = s.R * x + s.T + SymLat( c )
>>>>>>       }
>>>>>> ;
>>>>>>      save_
>>>>>> ======
>>>>>> 
>>>>>> Should that remain the same, or should it be as follows
>>>>>> 
>>>>>> ======
>>>>>> save_function.SymEquiv
>>>>>>      _definition.id              'function.SymEquiv'
>>>>>>      _definition.update           2007-10-11
>>>>>>      _description.text
>>>>>> ;
>>>>>>       The function
>>>>>>                       xyz' =  SymEquiv( symop, symcat, xyz )
>>>>>> 
>>>>>>       returns a fractional coordinate vector xyz' which is input vector
>>>>>>       xyz transformed by the input symop 'n_pqr' applied to the symmetry
>>>>>>       equivalent matrix extracted from the category symcat.
>>>>>> ;
>>>>>>      _name.category_id            function
>>>>>>      _name.object_id              SymEquiv
>>>>>>      _type.purpose                Assigned
>>>>>>      _type.container              Array
>>>>>>      _type.contents               Real
>>>>>>      _type.dimension              {3}
>>>>>>       loop_
>>>>>>      _method.purpose
>>>>>>      _method.expression
>>>>>>       Evaluation
>>>>>> ;
>>>>>>       Function SymEquiv( c :{Single, Symop},    # symop string n_pqr
>>>>>>                          l :{Category, Tag},    # loop of symmetry
>>>>>> matrices
>>>>>>                          x :{Array, Real}    )  # fract coordinate vector
>>>>>>       {
>>>>>>               s = l { SymKey( c ) }
>>>>>> 
>>>>>>               SymEquiv = s.R * x + s.T + SymLat( c )
>>>>>>       }
>>>>>> ;
>>>>>>      save_
>>>>>> ======
>>>>>> 
>>>>>> 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
>>>>>> =====================================================
>>>>>> 
>>>>>> _______________________________________________
>>>>>> 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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>>>>> ddlm-group@iucr.org
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>>>>> 
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>>> 
>>> 
>>> 
>> 
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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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