ALL_TACTactical.ALL_TAC : tactic
Passes on a goal unchanged.
ALL_TAC applied to a goal g simply produces
the subgoal list [g]. It is the identity for the
THEN tactical.
Never fails.
The tactic
INDUCT_THEN numTheory.INDUCTION THENL [ALL_TAC, tac]
applied to a goal g, applies
INDUCT_THEN numTheory.INDUCTION to g to give a
basis and step subgoal; it then returns the basis unchanged, along with
the subgoals produced by applying tac to the step.
Used to write tacticals such as REPEAT. Also, it is
often used as a place-holder in building compound tactics using
tacticals such as THENL.
Prim_rec.INDUCT_THEN,
Tactical.NO_TAC, Tactical.REPEAT, Tactical.THENL