FILTER_STRIP_THEN
Tactic.FILTER_STRIP_THEN : (thm_tactic -> term -> tactic)
Conditionally strips a goal, handing an antecedent to the theorem-tactic.
Given a theorem-tactic ttac, a term u and a goal (A,t),
FILTER_STRIP_THEN ttac u removes one outer connective (!, ==>, or
~) from t, if the term being stripped does not contain a free
instance of u. A negation ~t is treated as the implication
t ==> F. The theorem-tactic ttac is applied only when stripping an
implication, by using the antecedent stripped off. FILTER_STRIP_THEN
also breaks conjunctions.
FILTER_STRIP_THEN behaves like STRIP_GOAL_THEN, if the term being
stripped does not contain a free instance of u. In particular,
FILTER_STRIP_THEN STRIP_ASSUME_TAC behaves like FILTER_STRIP_TAC.
Failure
FILTER_STRIP_THEN ttac u (A,t) fails if t is not a universally
quantified term, an implication, a negation or a conjunction; or if the
term being stripped contains the term u (conjunction excluded); or if
the application of ttac fails, after stripping the goal.
Example
When solving the goal
?- (n = 1) ==> (n * n = n)
the application of FILTER_STRIP_THEN SUBST1_TAC "m:num" results in the
goal
?- 1 * 1 = 1
FILTER_STRIP_THEN is used when manipulating intermediate results using
theorem-tactics, after stripping outer connectives from a goal in a more
delicate way than STRIP_GOAL_THEN.
See also
Tactic.CONJ_TAC,
Tactic.FILTER_DISCH_TAC,
Tactic.FILTER_DISCH_THEN,
Tactic.FILTER_GEN_TAC,
Tactic.FILTER_STRIP_TAC,
Tactic.STRIP_ASSUME_TAC,
Tactic.STRIP_GOAL_THEN