PEXISTS_EQ : (term -> thm -> thm)
STRUCTURE
PairRules
LIBRARY
pair
SYNOPSIS
Existentially quantifies both sides of an equational theorem.
DESCRIPTION
When applied to a paired structure of variables p and a theorem whose conclusion is equational: 
    A |- t1 = t2

the inference rule PEXISTS_EQ returns the theorem: 

    A |- (?p. t1) = (?p. t2)

provided the none of the variables in p is not free in any of the assumptions. 

          A |- t1 = t2
   --------------------------  PEXISTS_EQ "p"      [where p is not free in A]
    A |- (?p. t1) = (?p. t2)

FAILURE
Fails unless the theorem is equational with both sides having type bool, or if the term is not a paired structure of variables, or if any variable in the pair to be quantified over is free in any of the assumptions.
SEEALSO
EXISTS_EQ, PEXISTS_IMP, PFORALL_EQ, MK_PEXISTS, PSELECT_EQ
HOL  Kananaskis-10