CONTR_TACTactic.CONTR_TAC : thm_tactic
Solves any goal from contradictory theorem.
When applied to a contradictory theorem A' |- F, and a
goal A ?- t, the tactic CONTR_TAC completely
solves the goal. This is an invalid tactic unless A' is a
subset of A.
A ?- t
======== CONTR_TAC (A' |- F)
Fails unless the theorem is contradictory, i.e. has F as
its conclusion.
Tactic.CHECK_ASSUME_TAC,
Drule.CONTR, Thm.CCONTR, Drule.CONTRAPOS, Thm.NOT_ELIM