Hi Jérémy, Thank you for your book! How you’re describing char-sets using a clear use-case looks really good! A few comments: # Try and run the test here you write “the test fails”, which is slightly unprecise. The precise wording would be “the test will fail to run”. # Write the minimal … I wonder why the test-suite returns "passes 1" in the second try (with undefined password-valid?). Jérémy Korwin-Zmijowski writes: > The next chapter will probably introduce macros (syntax-rules) ! If you want to see the extend to which you can play with macros, you can have a look at my natural-script-writing entry-point (from enter-three-witches): https://hg.sr.ht/~arnebab/dryads-wake/browse/enter.w?rev=tip#L349 Thank you for your book! Best wishes, Arne -- Unpolitisch sein heißt politisch sein ohne es zu merken