CHANGED_TAC

Tactical.CHANGED_TAC : (tactic -> tactic)

Makes a tactic fail if it has no effect.

When applied to a tactic T, the tactical CHANGED_TAC gives a new tactic which is the same as T if that has any effect, and otherwise fails.

Failure

The application of CHANGED_TAC to a tactic never fails. The resulting tactic fails if the basic tactic either fails or has no effect.

See also

Tactical.TRY, Tactical.VALID