op ORELSE : tactic * tactic -> tactic

SYNOPSIS
Applies first tactic, and if it fails, applies the second instead.

DESCRIBE
If T1 and T2 are tactics, T1 ORELSE T2 is a tactic which applies T1 to a goal, and if it fails, applies T2 to the goal instead.

FAILURE
The application of ORELSE to a pair of tactics never fails. The resulting tactic fails if both T1 and T2 fail when applied to the relevant goal.

SEEALSO  EVERY,   FIRST,   THEN

HOL  Kananaskis 0