I have seen code that only the programmer who writes it understands how it works. However, when one asks the programmer to explain what the code do...
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A really important part of the DRY principle is that you don't know that you need to make it DRY before it's already WET.
Until you've written both the A and B examples you don't know that you need a function. In simple examples like this you'll probably figure it out as you start writing B, but if you started out with the DRY example and only needed it once then you did that work for nothing.
The YAGNI really makes me laugh, that's exactly what I do and that's exactly what happen 😂
We, developers, have issues to NOT make extra helpers functions or variables that are useless!
Important to know that DRY is more about knowledge than code. Check this comment for a link to a /very/ interesting article