Trait vs inheritance; dispatch time

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My understanding of Rust Koans​​​​​ - #2 by DanielKeep is that it actually has nothing to do with traits vs inheritance, but everything to do with "do you have to list all traits/superclasses at time of defining a struct" ?

For example:

  1. Common Lisp Object System - Wikipedia definitely has a class hierarchy. I'm pretty sure the problem can be solved in CLOS.

  2. Even in plain Java, one can do "class BrotherFarbold implements interface CookingDuties"

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My understanding of that koan is that it makes two assumptions:

  1. with traits, you can add new traits later on

  2. with inheritance, you haver to define everything in inherit from up front when the class is defined

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I am not sure I agree with (2).