EXT
Drule.EXT : thm -> thm
Derives equality of functions from extensional equivalence.
When applied to a theorem A |- !x. t1 x = t2 x, the inference rule
EXT returns the theorem A |- t1 = t2.
A |- !x. t1 x = t2 x
---------------------- EXT [where x is not free in t1 or t2]
A |- t1 = t2
Failure
Fails if the theorem does not have the form indicated above, or if the
variable x is free in either of the functions t1 or t2.
Comments
This rule is expressed as an equivalence in the theorem
boolTheory.FUN_EQ_THM.