Ah, I see, though I'd say it pollutes the function namespace a bit this way (as "in-x" semantically only makes sense in a loop) and missing on-list. Technically, you could do most of these in a few lines of CL too, but well, convenience is the point of these macros.

Those seem to return sequences instead of streams/iterators, any idea why? Though it says "An in-list application can provide better performance for list iteration when it appears directly in a for clause", so I guess there's some macro magic at play.

Anyway, thanks for exposing those, Racket does seem to be pretty practical (and with its Chez backend, I guess it's pretty fast); can't stand the square brackets used as syntax (as opposed to vector literals used as data), though ¯\_(ツ)_/¯.