Do you know about any "Factor for Forth programmers" tutorial? Factor is similar enough to irritate me with it's "for beginners" materials, but different (and larger) enough to make normal manuals useless by themselves.

I'd especially appreciate a bottom-up write up, starting with the stack and cells (which feel familiar), and then introducing higher-level abstractions of Factor.

Better wash your brain about that implied misconception. Factor is much more like Lisp and Haskell (esp point-free style) than Forth. I guess "learn Lisp and/or Haskell and Factor won't seem so foreign" isn't terrific advice. But right now there doesn't exist many newbie guides at all.

I dunno, syntactically it resembles Forth quite a bit, what with : ; for defining words and () for comments and all that. Anyway, I have no problem whatsoever with high-level abstractions in Factor, nor with its concatenative nature, nor with its macros and so on. I know all these features from other languages. What I want is a just description of how these high-level things map to assembly, I guess. For example I just learned that: "Internally, a quotation is a pair, consisting of an array and a machine code entry point. The array stores the quotation's elements" - this is a kind of definition I want for all the abstractions in Factor. It's probably best to go through Slava Pestov blog and pick up such scattered descriptions, but I'd really appreciate if someone prepared a single article with all these definitions.

Note that the stack comments aren't actually comments in Factor - they're part of the function definition and are mandatory. The compiler will do a simple check to ensure that all of your stack inputs and outputs match up for each function call.

We made stack effects mandatory for most definitions as it appeared an area of frustration with new Factor programmers.

However, we have a stack checker that still supports optional stack effects if you yearn for the good ol' days:

https://github.com/slavapestov/factor/issues/887