Is there a good blogpost/writeup on this idea? I've seen it mentioned before in other threads.... And i agree 100%

From John Carmack:

http://number-none.com/blow/blog/programming/2014/09/26/carm...

That's a for a specific case of high performance code and removing duplicated work.

Referencing carmwack always has to be in the context of high performance code.

Even carmack himself has started like functional code. Which normally leads you down small pure functions.

No, that is not for a specific case of high performance... It's for the non-specific case of keeping the code clear, understandable, and bug-free. The style was chosen for these reasons, not because it is more performant. It just happens to also be more performant than the layers of indirection that also harm understandability.

For a procedural code base, avoid subprocedures that are only called once.

For a pure functional codebase, e.g. Haskell, locally-scoped single-use functions can be beneficial.

Clean Code is still a great read in 2020, but I think you’re right about some of the specific advice about functions.