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Re: [ddlm-group] List/table recursion limits?

Function invocations aside, the actual recursive depth for given data file 
conforming to a set of dictionaries is determined by the types of the 
list, array and table typed tags in those dictionaries.  At the moment, 
the worst depth seems to be 2 for import lists and 2-D arrays.  For 
Fortrans without dynamic array allocation, you do have to preset such 
depths (with parameter statements).  To detect runaways in the parser, I 
did a lot of debugging of CIFtbx 4.1.0 with a depth limit of 3, but so as 
not to have to worry about it in production use, the current limit is set 
at 20.

Fortran is not practical for direct method invocation, so some static 
depth limit greater than or equal to 3 should suffice for the immediate 
furuter.  For python or C, which are a more appropriate environment for 
method invocation, there is no need for a specific depth limit, and, as 
Nick points out, you could end up going very deep, so a hard limit is 
likely to cause trouble.

I would suggest not imposing a specific limit, and leave that as a 
configuration detail for setting up software to be able to deal with 
specific scientific domains.  Even for Fortran, it is easy enough to 
change a parameter (in my case MAXDEPTH) when necessary.

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


On Mon, 7 Dec 2009, Nick Spadaccini wrote:

> On 5/12/09 4:30 AM, "Joe Krahn" <krahn@niehs.nih.gov> wrote:
>> It may be useful to put practical limits on recursion depth. Maybe 8 is
>> sufficient? I suspect that most CIF developers want to keep nesting
>> fairly shallow, given that CIF disallows and STAR loop nesting.
> Is it necessary to apply a restriction to the recursive depth? As you say
> humans will keep it fairly shallow anyway to keep things clear, but I can
> foresee a machine generated data value being quite deep.
> If I was to output as a CIF2 value (not that I would ever do this) the
> entire internal representation of a domain dictionary category (and its
> attributes), including methods and data file values, it would be a deeply
> recursive compound data structure of significant complexity. But it would
> all fit in a Table.
> cheers
> Nick
> --------------------------------
> Associate Professor N. Spadaccini, PhD
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