Re: Tidying up DDL1

[Matthew Towler <towler@xxxxxxxxxxxxxx>]

> _enumeration_range:  "can apply to 'numb' or 'char' items which
> have a preordained sequence"; is this meant to
> include Mon:Fri, June:Sept etc?  From a programming point of
> view the range of application needs to be circumscribed, and
> I would argue for restricting it to numbers only, which is consistent
> with use in current DDL1 dictionaries.  For small sets,
> such as letters, we can just list them.  We do this for the
> element symbols, rather than just write _enumeration_range 'H':'U'

I agree.  The whole point of dictionaries is that the program using them 
does not have to know about types a-priori.  Listing just the terminal 
values and expecting a program to insert the 'preordained' values goes 
directly against this principle.

> I note that *_gt and *_lt data
> names have appeared for situations that could have been covered by
> constructions of the type a:b. 

I think the intention of the *_gt and *_lt data names was to cover cases 
  such as "greater than 400 kelvin".  The issues being to represent both 
an unbounded range in one direction and one that does not include the 
bounding value.  The addition of the *_gt and *_lt data has the 
advantage that it does not require changing the CIF standard, but the 
disadvantages that it is not a general solution to a recurring problem, 
and that it significantly complicates the reading of data from a CIF.

Matthew

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