iRel interface updates

[James Porter]

I've been working on implementing the new(ish) iRel interface in Lasso
and after some discussion with Tim Tautges, we've proposed a few small
changes to the interface. Attached is the new header plus a diff. Here's
what changed, in descending order of importance:

* Removed iRel_getRelatedInterfaces in favor of iRel_findRelations,
  which takes an interface as input and returns an array of
  iRel_RelationHandles, which can then be queried with
  iRel_getRelationInfo

* Added interface type parameters to iRel_getRelationInfo, so that users
  of this function can be sure they have, say, an iMesh interface. This
  also makes the function more consistent with iRel_createRelation (the
  inputs of one would be the outputs of the other, and vice versa).

* Re-added iRel_getSetEntRelation and friends, since otherwise there's
  no way to pass in a set and get a related entity

* Moved iRel_newRel to the top of the file to match iMesh and iGeom

* Minor changes to documentation

Another change I'll suggest but have no strong attachment to is that we
change iRel_RelationHandle to iRel_PairHandle to make a distinction
between the relation of two interfaces (a "pair") and the relation of
entities/sets (a "relation"). The changes would be as follows:

* iRel_RelationHandle  -> iRel_PairHandle
* iRel_createRelation  -> iRel_createPair
* iRel_destroyRelation -> iRel_destroyPair
* iRel_getRelationInfo -> iRel_getPairInfo
* iRel_findRelations   -> iRel_findPairs

Does anyone have any comments on these changes (either in the attachment
or above)? Ideas? Complaints?

Thanks,
Jim
-------------- next part --------------
A non-text attachment was scrubbed...
Name: iRel.h
Type: text/x-chdr
Size: 22275 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/tstt-interface/attachments/20100708/cdc92913/attachment.h>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: diff
Type: text/x-patch
Size: 8131 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/tstt-interface/attachments/20100708/cdc92913/attachment.bin>