A logical expression specifying a program state that must exist or a set of conditions that program variables must satisfy at a particular point during program execution;for example, A is positive and A is greater than B.

• 一种逻辑表达式,它规定必须存在的一个程序状态,或规定在程序执行过程中某一特定点上程序变量必须满足的条件集合;例如,A为正且A大于B。