又学了一招
把\mid改成\middle\vert就可以适应高度了,比如:
\begin{align*}
\mathcal{D}(A):=\left\{X \subseteq A\ \middle\vert\ \begin{array}3\exists n\ \exists s \in A^n\ \exists R \in {\operatorname{Def}(A,n+1)} \\ \text{s.t.}\ X = \{a \in A \mid (a,s_0, \dotsc, s_{n-1}) \in R\}\end{array}\right\}
\end{align*} |