dest_exists1
boolSyntax.dest_exists1 : term -> term * term
Breaks apart a unique existence term into quantified variable and body.
If M has the form ?!x. t, then dest_exists1 M returns (x,t).
M
?!x. t
dest_exists1 M
(x,t)
Fails if M is not a unique existence term.
boolSyntax.mk_exists1, boolSyntax.is_exists1
boolSyntax.mk_exists1
boolSyntax.is_exists1