1. Class ends at 6pm
2. Zoom call scheduled at 7pm
3. Train from campus to home at 5:45pm
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Not clear whether I can reach home in time



type funnyList = FunnyNil | FunnyNode of int * funnyList
// Claim 1: A value of type funnyList might look like a FunnyNil
// Claim 2: A value of type funnyList might look like a FunnyNode.
            In this case, it will have an integer and another funnyList
// Claim 3: (Closed world) A value of type funnyList cannot look like anything else

// Open world
sealed abstract class FunnyList
class FunnyNil extends FunnyList
class FunnyNode extends FunnyList
...