How to add an auxiliary variable but not increase the state space?

[Guo Hua]

In TLA+, when I add my auxiliary variable "history," the specification behaviors depend on the  "history" variable, and the state space would increase.
Can I specify the specification next state behavior does not depend on the auxiliary variable, and the additional variable does not increase the state space?

[Hillel Wayne]

You'll want to define a custom VIEW, see https://learntla.com/topics/toolbox.html#additional-tlc-options

On Tue, Nov 8, 2022, 9:54 AM Guo Hua <fch...@gmail.com> wrote:

In TLA+, when I add my auxiliary variable "history," the specification behaviors depend on the  "history" variable, and the state space would increase.
Can I specify the specification next state behavior does not depend on the auxiliary variable, and the additional variable does not increase the state space?

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[Leslie Lamport]

Changing the view won't hurt.  But a history variable h is generally added by conjoining to each action a formula of the form h' = ... .  Doing that doesn't add any states; it just adds a new component to each state.  That shouldn't significantly increase TLC's running time, and little of any increase in running time will be saved by the view change.

Leslie

[Leslie Lamport]

Forget what I just wrote.  I don't know where my brain was when I wrote it.  Yes, use view.

Leslie

[Guo Hua]

Thank you for your reply. View works.

[Guo Hua]

Thank you for the answer. Using view solves the problem.