Quack

Quack enhances Emacs support for Racket and Scheme.

Note: Quack is getting old, but still useful. I implemented most of a replacement for Quack, called Meow, which does a proper parse rather than use Regexp kludges, but got interrupted and didn't finish it. For now, if you're using Racket, you probably want to use Greg Hendershott's racket-mode.

You can download file quack.el, version 0.48 (2016-04-03).

Quack is included in Linux distributions Debian (package emacs-goodies-el in testing) and Gentoo (port app-emacs/quack).

Main screenshot for Meow, Quack's possible someday replacement.

Meow even parses quote shorthand (even pathological multiple quotes), and can do intuitive structural navigation for it.

When Meow uses bright red to highlight a parse error (and recover from it), it can display a diagnosis of the parse error using a hover tooltip.

(If I ever dust off Meow, it will be for portable Scheme, and will get rid of the Racket-idiomatic red for parentheses, by default.)