Changes by: Aleksey Nogin (nogin at cs.caltech.edu)
Date: 2006-02-13 02:44:17 -0800 (Mon, 13 Feb 2006)
Revision: 8676
Log message:
"Strong" elimination rules (dprod, prod, disjoint union) should be formulated
in thinning form; it should be up to the user and/or tactic to copy the hyp if
it needs to be preserved (which is never the case in existing proofs).