Exercise 5.9 · 习题

Exercise 5.9: The treatment of machine operations

above permits them to operate on labels as well as on constants and the

contents of registers. Modify the expression-processing procedures to enforce

the condition that operations can be used only with registers and constants.

练习 5.9：上面对机器操作的处理允许它们同时作用于标号、常量以及寄存器的内容。修改表达式处理过程，强制规定操作只能与寄存器和常量一起使用。