CL21 and thoughts on a modern lisp

I agree with you re. array and hash table literals. We already have list literals; adding arrays and hash tables would be great. Fortunately, they could be added with some simple read macrods; I suggest #[] and #{}.

By 'slice,' I assume you mean Python-like slices, not Go-like slices (which are for our purposes adjustable arrays, which CL has); what's wrong with (subseq array start end)?

Yes, string manipulation could be much better. I personally always define a STRCAT which is really just (concatenate 'string …). I'm actually a bit excited by some of the interpolation ideas out there. I definitely don't want to lose FORMAT though.

I actually like the pathnames API, but it could stand to be better-specified for the common Unix case.

Agreed on more batteries included.

I don't mind packages (in fact, find them highly useful), but would like a standard system definition facility. What do you find lacking with respect to packages?

It definitely needs to default to either downcasing or case-preserving. Upcase is so ugly. Do note that character encoding appears to be a solved problem; the Lisps I use are quite comfortable with Unicode.