@JosephWright It looks like my error last night was simply that I forgot to pass the -shell-option. As often is the case, the obvious is the easiest to overlook.
I wonder if there is some easy way to flag that particular error.
@UlrikeFischer That one is stable: I meant \seq_set_from_function:NnN, \seq_set_from_inline_x:Nnn, \seq_indexed_map_...; not sure what to do with the mapthread one (we likely do want it, name is awkward)
@UlrikeFischer For me yes instead, because it is a sign of respect and appreciation. Unfortunately in this period I am very busy with the school and worried because some students of a new classroom of this year that not remember anything about Mathematics and Physics.
@JosephWright while reading yesterday the description of the casing commands I thought that the general concept fits also for "tl to pdf-string-for-bookmarks", something like \tl_pdfstring_case:n. Almost everything that pdfstringdef has to do (exceptions, commands, math) is more or less there.
@UlrikeFischer I just sent something around for 'Team meeting 27/09'
@UlrikeFischer Oooh, I'd not thought about that: perhaps we should discuss in light of the hyperref business: could have a 'no change of case' function using the same mechanism
@JosephWright well it is not really a "no change" function, as one wants to get unicode (e.g. currently something like \000\040\330\076\335\206, and we should drop pdfdocencoding), but if one generalize the idea of "casing" I think one can reuse lots of your code here.
@UlrikeFischer Sure: I meant that the mechanisms set up in the case-changing code all work by expansion. But one could do things in two stages: first 'make safe' then 'escape'
@FaheemMitha Many doctors have recommended yoga to me. But I have many commitments. And then I'm angry because I have a class that doesn't remember anything about mathematics-physics (they're 16 years old) and I'm in total panic. I should also create slides with beamer or ppt but with all sincerity I can not sit down. In fact, in a while I'll be out of TeX.Se and I'm going around for a walk.
@Sebastiano I don't think the question is really answerable, what answer do you want other than put \label{zzz} in the item and reference it with \ref{zzz}
@DavidCarlisle In fact I'm asking every user if he has a greater creativity than my current one to have a more attractive and beautiful numbering list to see. I'm not good in English and I hope it's been clearer now. You can edit my question freely.