X_CHOOSE_TAC : term -> thm_tactic
A ?- t =================== X_CHOOSE_TAC y (A1 |- ?x. w) A u {w[y/x]} ?- t (y not free anywhere)
{n < m} ?- ?x. m = n + (x + 1)the following theorem may be applied:
th = [n < m] |- ?p. m = n + pby the tactic (X_CHOOSE_TAC (Term`q:num`) th) giving the subgoal:
{n < m, m = n + q} ?- ?x. m = n + (x + 1)