[mcclim-devel] question about implementation detail in format-graph-from-roots

[rpgoldman at real-time.com]

Some questions about the implementation details:

1.  I was just noticing that the hash-table that is used for duplicate
detection is only used in the generate-graph-nodes method, but is kept
as a slot in standard-graph-output-record.  Is there any reason I
shouldn't turn this into a local variable in generate-graph-nodes?
I'm concerned that, for large graphs, this could end up being a pretty
large piece of uncollectable garbage.  It might be even worse if the
duplicate-test argument forces us to have a node list instead of a
hash-table.  

I suppose if I do this, then we might get away with not keeping
duplicate-test and duplicate-key in the graph-output-record objects,
either...

2.  Can anyone explain to me why :duplicate-test and :duplicate-key
are keyword arguments to generate-graph-nodes but :merge-duplicates is
not?  Seems odd...

3.  The existing code has the following lambda list for
FORMAT-GRAPH-FROM ROOTS:

(root-objects object-printer inferior-producer
                                &rest graph-options
                                &key stream orientation cutoff-depth
                                     merge-duplicates duplicate-key duplicate-test
                                     generation-separation
                                     within-generation-separation
                                     center-nodes
                                     (arc-drawer #'clim-internals::standard-arc-drawer)
                                     arc-drawing-options
                                     graph-type (move-cursor t)
                                &allow-other-keys)

then has the following immediately below:

  (setf stream (or stream *standard-output*)
        graph-type (or graph-type (if merge-duplicates :digraph :tree))
        duplicate-key (or duplicate-key #'identity)
        duplicate-test (or duplicate-test #'eql) )

Could we have duplicate-key and duplicate-test simply get their
defaults in the lambda-list?  Or is this not feasible because of the
GRAPH-OPTIONS &rest argument?

Thanks,
Robert