Talking about code repetition is focusing on the wrong thing, consider how metaprogramming is used in the article: it mechanically generates the same code that

Talking about code repetition is focusing on the wrong thing, consider how metaprogramming is used in the article: it mechanically generates the same code that previously was simply in place in the class. It doesn't make anything simpler to understand, it doesn't allow to modify common logic in one place and in the future it is likely those common "behaviours" will diverge anyway because the similarity is just very weak and superficial. I would instead advise to strive to extract all possible interesting abstractions and if you pushed yourself really hard to do it and there is some repeated code left at the end, it might just be fine to leave it as it is - the cost of removing duplication might outweigh the benefit. In the example posted, position and direction are both vectors, recognizing them as such would provide a much better way of checking for "zeroness" and for negation. It's a nice educational aspect of this toy problem the author seems to not have noticed himself. There is often a similar elegant way out of real-world complex problems that doesn't involve fancy meta-programming but just good abstractions, putting right data in the right place etc.