Switch to `racket/base', change some "~e"s to "~.s"s, also reformat and a few minor improvements.
Switch to `racket/base', change some "~e"s to "~.s"s, also reformat and
a few minor improvements.

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket