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*From*: "c.burge...@xxxxxxxxx" <c.burge.glasgow@xxxxxxxxx>*Date*: Fri, 30 Apr 2021 06:09:30 -0700 (PDT)*References*: <f06df008-8efa-4942-bb93-a2ebbbfe7984n@googlegroups.com> <09E12A1A-7A9E-4A1D-9B43-7048C57AE425@gmail.com>

Thanks, clearly it doesn't help when I get my logical syntaxes confused!

I now have:

(y=0 /\ y' = 0) \/ (y # 0 /\ y' = y-1)

But when I put this as a property in TLC, I get the error:

"The property ... is not correctly defined."

On Friday, April 30, 2021 at 1:48:03 PM UTC+1 Stephan Merz wrote:

Hello,1. "not equal" is written # in TLA+ (or /=), "~" is Boolean negation.2. I believe "->" represents implication in your formula, but it is written "=>" in TLA+.3. The expressions on both sides of an implication should be Boolean, but the _expression_ on the right-hand side is y-1.4. The (action) formula corresponding to your informal statement can be written as\/ y' = 0\/ y # 0 /\ y' = y-1A similar formula (but with a slightly different meaning) isy' = IF y # 0 THEN y-1 ELSE 0StephanOn 30 Apr 2021, at 14:39, c.burge...@gmail.com <c.burge...@xxxxxxxxx> wrote:Hi again!

I have the following temporal formula:y'= 0 \/ y ~0 -> y-1

Which I hope says that the next value of y is zero or y-1 if y is not zero.

However, when I put this as a property in TLC, I get the error:

Was expecting ===== or more module body, encountered '~' in Properties at line 1 and token 'y'.

Obviously it's not happy with the ~ (equally unhappy with \lnot), but I'm not sure how to proceed from here!--

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**Follow-Ups**:**Re: [tlaplus] What's wrong with this temporal formula?***From:*Stephan Merz

**References**:**[tlaplus] What's wrong with this temporal formula?***From:*c.burge...@xxxxxxxxx

**Re: [tlaplus] What's wrong with this temporal formula?***From:*Stephan Merz

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