9
Least Fixpoint
•
Fix
U = a finite set
•
Definition
Let F : P(U)
!
P(U).
A fixpoint
for F is X
µ
U s.t. F(X) = X
•
•
Definition
The least fixpoint is some X s.t. for
every other fixpoint Y, X
µ
Y
•
•
Notation
:
lfp
(F)