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[tlaplus] Question about the value of action expressions
I would like to check my understanding of a simple TLA+ concept that I now find confusing.
Say we have the action:
A == /\ x = 5
/\ x' = 7
I understand that the equals sign in TLA+ is not an assignment but an equality check, so it's clear to me why 'x = 5' returns a boolean.
What I'm less clear about is the second line. My understanding is that it assigns the value of x in the next state as 7, and the line evaluates to True if x has not already been assigned in the next state. Is that right?
I'm confused because the equality check in this case is performing an assignment, while also seemingly evaluating to a boolean. I'm assuming it evaluates to a boolean value here because it's used with the AND operator. Am I thinking about this in the wrong way?
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