Exam question: 31.08.2021 How did we get the step from green to yellow?

Question

In the first screen shot, How did we get the step from green to yellow , considering that the second (blue highlighted) rule in the second screen shot better fits the step (since low of node is 0)?

Comments

I see that you like the rewrite rules better than the algorithm. Nice to see, that I have made them for some purpose.

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Yes, Professor, the rewrite rules are much easier to use than the algorithms. Thank you for those!

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Same here, find rewrite rules much easier to understand.

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The example solution has been adapted accordingly. Thanks for pointing this out.

Answer 1

I agree that the solution is weird even though the result is correct. This one is a better solution: 

Constrain(beta2,phi2)
    = Constrain((a?beta4:beta3),(a?true:phi3))
    = (a ? Constrain(beta4,true) : Constrain(beta3,phi3))
    = (a ? true : Constrain(beta3,phi3))
    = (a ? true : Constrain((b?true:beta5),phi3))
    = (a ? true : (b ? Constrain(true,phi3) : Constrain(beta5,phi3) ))
    = (a ? true : (b ? phi3 : Constrain(beta5,phi3) ))
    = (a ? true : (b ? phi3 : Constrain((c?true:false),(c?false:true)) ))
    = (a ? true : (b ? phi3 : Constrain(true,false) ))
    = (a ? true : (b ? phi3 : false ))

Do you agree with this one?

Comments

Yes Professor, this makes more sense. Thank you.