Strictly speaking, a particular stack is an instance not of STACK (which, as noted, is a type pattern rather than a type) but of some type generically derived from STACK, for example STACK [ACCOUNT].

• 严格来说，一个精确的栈不但是一个STACK（如上所述,这是一个类型模式而非一个类型）的实例而且是从STACK派生出的一些泛化类型的实例，如STACK[ACCOUNT]。