X_GEN_TAC : (term -> tactic)
STRUCTURE
SYNOPSIS
Specializes a goal with the given variable.
DESCRIPTION
When applied to a term x', which should be a variable, and a goal A ?- !x. t, the tactic X_GEN_TAC returns the goal A ?- t[x'/x].
     A ?- !x. t
   ==============  X_GEN_TAC "x'"
    A ?- t[x'/x]

FAILURE
Fails unless the goal’s conclusion is universally quantified and the term a variable of the appropriate type. It also fails if the variable given is free in either the assumptions or (initial) conclusion of the goal.
SEEALSO
HOL  Kananaskis-10