Many loop invariants can be expressed in the form of the fixed point of a predicate universal function while weakest precondition is least fixed point and explained in the view of category theory.

• 在此基础上引入不动点原理深入刻划循环不变式的含义，循环不变式可以表示为谓词泛函的最小不动点，并从范畴论的角度解释该过程。