MK_EXISTSDrule.MK_EXISTS : (thm -> thm)
Existentially quantifies both sides of a universally quantified equational theorem.
When applied to a theorem A |- !x. t1 = t2, the
inference rule MK_EXISTS returns the theorem
A |- (?x. t1) = (?x. t2).
A |- !x. t1 = t2
-------------------------- MK_EXISTS
A |- (?x. t1) = (?x. t2)
Fails unless the theorem is a singly universally quantified equation.
Thm.AP_TERM, Drule.EXISTS_EQ, Thm.GEN, Drule.LIST_MK_EXISTS,
Drule.MK_ABS