Types and Programming Languages习题的参考解答及思考(第23章)

第23章 章节23.4 练习23.4.1 题目: Using the typing rules in Figure 23-1, convince yourself that the terms above have the types given. \[ \begin{aligned} &\text{id} = \lambda \text{X. } \lambda \text{x}: \text{X. } \text{x}; \\ \blacktriangleright \text{ } &\text{id} : \forall \text{X. } \text{X} \to \text{X} \end{aligned} \] \[ \begin{aligned} &\text{id} \text{ } [\text{Nat}];