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*From*: Shuhao Wu <shuhao@xxxxxxxxxxxx>*Date*: Mon, 28 Jun 2021 16:06:54 -0400*Ironport-hdrordr*: A9a23:4p0JqaFpqxcykTwjpLqF6pHXdLJyesId70hD6qkvc3AlCvBwxvrC7Y0mPEHP4kd2ZJhSo6HNBEDmewKSyXcV2/hdAV7GZmbbUQSTXchfBOfZskrd8mjFh6RgPUkJSdknNDXfZWIK1PoSozPIVurJ+bG8geaVbJ7lvixQpGJRGupdB7ITMHfYLqQVfngxOXNjLuve2iMvnVPJEgVyH7/Lewh4Lpv+SsXw5ejbiFw9dmoaAW+1/HOVAZHBciRwtS1uIQ+nr41ShFQt3zaJrplKcpmAu3rhPqzoj6i+WuGO9jPyb/b8zfT95g+c6TqAVcBEd/m6pzYlsIiUmSYXueiJhztlBt90+mOUVGmouxeF4XiQ7B8er1vPjWSVi3fivsD1LQhKdfZptMZ8Xl/i500ssMoU6tM144qV3KAnTC8pbE/Glpb1vthR5yjExkYKoKoolnRaFaEeZLVSoYFa3EQQPowHADuS0vFiLNVT*References*: <16569f5a-d5fe-01d9-196a-c5e76adaaaed@shuhaowu.com> <7668376b-91f4-1caa-18e2-186585cd4835@lemmster.de>*User-agent*: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0

TwoRemainsTwo == []((i = 2) => [](i = 2))

(i = 1) ~> (i = 2) /\ []((i = 2) => [](i = 2))

Thanks, Shuhao On 2021-06-28 3:33 p.m., Markus Kuppe wrote:

On 6/28/21 12:01 PM, Shuhao Wu wrote:I've been trying to write a temporal property to check in TLC where Iwant to know that some condition F leads to G, and G remain true forthe rest of time. This lead me to using the temporal operators ~> and[] together, in a statement in the form of F ~> []G. I'm likelymisunderstanding one of these operators, as when I used TLC to checkthe following simple spec, the nothing was found to be violated:--fair algorithm leadstoalways variables i = 1; define \* This is the temporal property to check OneLeadsToTwo == (i = 1) ~> [](i = 2) end define; begin step1: i := 2; step2: i := 3; step3: i := 2; end algorithm;My understanding is that (i = 1) ~> (i = 2) would be true for theabove program (which is true in TLC). In the same understanding, (i =1) ~> [](i = 2) would not be true, as the variable i changed from 1 to2, then away from 2, and then back to 2. This means that i = 2 is notalways true following the initial transition from i = 1 to i = 2.What am I missing?Leads-to (P ~> Q) is "syntactic sugar" for [](P => <>Q) (see page 91of Specifying Systems).M.

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