4
Computing Types
•
Theorem
There exists an IFP formula
f
(
x
,
y
)
s.t.
8
a
,
b
2
A
k
,
a
¼
b
iff A
²
f
(
a
,
b
)
•
•
•
Proof
Will compute the negation,
a
À
b
as an
IFP formula
(should be not
¼
)
•
•