TLA+ error : The invariant Invariants is not a state predicate

Question

在我的规范中，我试图检查序列中的变化是 -1、0 还是 1。

我将这个不变量描述如下：


PVariance == Len(waitingRoomP') - Len(waitingRoomP) \in {-1,0,1}
CVariance == Len(waitingRoomC') - Len(waitingRoomC) \in {-1,0,1}

Invariants ==
    /\ TypeInv
    /\ \/ PVariance 
       \/ CVariance

TLC 模型检查器输出如下：

The invariant Invariants is not a state predicate (one with no primes or temporal operators).
Note that a bug can cause TLC to incorrectly report this error.
If you believe your TLA+ or PlusCal specification to be correct,
please check if this bug described in LevelNode.java starting at line 590ff affects you.

Answer 1

waitingRoomP'是下一个状态下waitingRoomP的值，意思是PVariance现在是一个动作。不变量不能是动作，它们只能是“纯”运算符。

您可以通过编写 [][PVariance]_waitingRoomP 来检查 PVariance 作为一个动作属性。这需要在工具箱中作为时间属性检查，而不是不变量。

TLA+ error : The invariant Invariants is not a state predicate

TLA+ error : The invariant Invariants is not a state predicate

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