# 不动点定理

## 离散数学和理论计算机科学领域

λ演算的共同主题是找到给出λ表达式的不动点。每个λ表达式都有一个不动点，不动点组合子是一个“函数”，即输入一个λ表达式并输出该表达式的一个不动点。一个重要的不动点组合是Y组合子，它使用递归定义。

## 脚注

1. ^ The foundations of program verification, 2nd edition, Jacques Loeckx and Kurt Sieber, John Wiley & Sons, ISBN 0-471-91282-4, Chapter 4; theorem 4.24, page 83, is what is used in denotational semantics, while Knaster–Tarski theorem is given to prove as exercise 4.3–5 on page 90.

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