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\DOC UNWIND_CONV
\TYPE {UNWIND_CONV : term -> thm}
\SYNOPSIS
Eliminates existentially quantified variables that are equated to something.
\KEYWORDS
conversion.
\DESCRIBE
The conversion {UNWIND_CONV}, applied to a formula with one or more existential
quantifiers, eliminates any existential quantifiers where the body contains a
conjunct equating its variable to some other term (with that variable not free
in it).
\FAILURE
{UNWIND_CONV tm} fails if {tm} is not reducible according to that description.
\EXAMPLE
{
# UNWIND_CONV `?a b c d. b = 7 /\ 2 = d /\ a + b + c + d = 97`;;
val it : thm =
|- (?a b c d. b = 7 /\ 2 = d /\ a + b + c + d = 97) <=>
(?a c. a + 7 + c + 2 = 97)
# UNWIND_CONV `?w x y z. w = z /\ x = 1 /\ x + y = z /\ y = 42`;;
val it : thm = |- (?w x y z. w = z /\ x = 1 /\ x + y = z /\ y = 42) <=> T
# UNWIND_CONV `x = 2`;;
Exception: Failure "CHANGED_CONV".
}
\SEEALSO
FORALL_UNWIND_CONV.
\ENDDOC
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