@felix9: Well he did say that writing De Bruijn indices has become a way of life ... what can that be used for?  I thought something like Wolfram Alpha - expression rewriters, automated formula manipulation, theorem provers etc....http://en.wikipedia.org/wiki/De_Bruijn_index.  That would fall into the Tangram space, as well.  However, Bart wouldn't bite and give me more hints when I asked. Wink