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*From*: mmynsted <code@xxxxxxxxxxxxxxxxxx>*Date*: Mon, 27 Jul 2020 12:48:07 -0700 (PDT)*References*: <25239a98-d60c-4d15-ad4f-6cce4964691fo@googlegroups.com> <c14403e0-1e14-4a45-8d3a-b8815c478781o@googlegroups.com>

Thank you.

For some reason if I do not bind the CHOOSE like:

x == CHOOSE a \in S : a \notin {}

Then I get an error "TLC attempted to evaluate an unbounded CHOOSE"

So something like this is closer to what I am after.

F[n \in Nat] == 0 .. n

S(n) == F[n]

P(Q) == CHOOSE n \in S(Cardinality(Q) + 1) : n \notin Q

Red == P({})

Yellow == P({Red})

Green == P({Red, Yellow})

Foo == P({Red, Yellow, Green})

I will try to simplify that F, S, and P bits... It seems like I should be able to use LET, In to combine those into a single operator.

On Monday, July 27, 2020 at 1:00:34 PM UTC-5 Leslie Lamport wrote:

If your spec contains a definition of the formx == CHOOSE b : b \notin Sthen when you create a model for it, the Toolbox will add to the model the appropriate

incantation to substitute for x a model value named "x". You could therefore writex == CHOOSE a : a \notin {}y == CHOOSE a : a \notin {x}z == CHOOSE a : a \notin {x,y}and you won't have to do any instantiation of constants.Leslie

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**Follow-Ups**:**[tlaplus] Re: Variables with values unspecified but distinct from each other***From:*Leslie Lamport

**References**:**[tlaplus] Variables with values unspecified but distinct from each other***From:*mmynsted

**[tlaplus] Re: Variables with values unspecified but distinct from each other***From:*Leslie Lamport

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