Re: [tlaplus] Questions about TLA+ formula.

[Stephan Merz <stephan.merz@xxxxxxxxx>]

Hello,

> On 25 Apr 2022, at 04:26, 宏黄 <wpkzxp@xxxxxxxxx> wrote:
> 
> Hi all.
> I'm reading the TLA+ hyperbook ，And I met some questions.
> In Chapter 17 Temporal Logic Question 17.5
> How to prove []p=>p' is not equivalent to any legal TLA+ formula.

hint: all temporal formulas of TLA+ are insensitive to inserting or removing stuttering steps.

> and  in Chapter 17.4.1 lead to 
> How to understand  F~>false,i think it is nerver true,when F is true,false do not become true

F ~> FALSE asserts that if F ever becomes true, then FALSE must be true eventually. Since the latter is impossible, the formula expresses that F can never become true. You would normally write this as []~F, but the formulation using leads-to is more convenient in the context of reasoning about leads-to properties.

Hope this helps,
Stephan

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