(I know you meant post at the top level, but I don't do that and don't have time to look up the rules for doing that.)
https://github.com/skx/critical/
It's a little addictive writing toy-interpreters for various (older and simpler) languages.
I think Tcl(’s standard library) is still too wordy to make a comfortable interactive shell, but it’s still leagues above everything else I’ve seen; in particular, I can’t help but think Shivers’s dismissal of interactive use in his description of Scsh is something of a cop-out—there are (now, maybe not then) plenty of nice languages to hack a prototype or a quick script in, but somehow Bourne shell + Unix utilities is still the best we can do that won’t make my fingers ache? Tcl demonstrates very well that inside sh there’s a Lisp trying to get out (and Plan 9’s rc does the same but worse), but somehow that line of thought seems to not have been continued further.
(Just in case, I see both Elvish and PowerShell as being more in the Scsh direction than the Tcl direction, that is making a “proper” language at the expense of interactive use and my fingers; Elvish appears to at least have a properness-Bourneness knob but that’s hardly a solution. Anyhow, I don’t think either contributes much to our knowledge of the virtually untouched interactive-use landscape, as opposed to the relatively well-explored scripting-language landscape.)
[1] http://yosefk.com/blog/i-cant-believe-im-praising-tcl.html
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