Re: Source code formatter?

[Lassi Kortela]

> The problem with pretty printer is that it is not designed for source:
> it does not keep comments and blank lines.

+1

Scheme reader that preserves them:

- https://github.com/weinholt/laesare

Work-in-progress formatters:

- https://github.com/paines/scmfmt (uses Chicken pretty printer)

- https://github.com/lispunion/code-formatter

Chez Scheme, Gambit, Gauche, Chibi-Scheme also ship a pretty-printer.

At the moment, most people probably use indent-region in Emacs. Emacs 
can also run in batch mode. There's probably something similar for Vim.

If any one feels like solving the problem for real, I'm happy to advise. 
This is the outline:

- Expand a reader like laesare to cover all the variants of S-expression 
syntax (Scheme, CL, Emacs Lisp, Clojure are very similar; no sense in 
having a different algorithm for each).

- Add a matching printer by consulting "the literature". Marc Feeley of 
Gambit has written a popular pretty-printer. Wadler has written a paper 
from first principles: 
<http://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf>.

- A good pretty printer should automatically figure out where to put 
line breaks, joining and splitting lines of code as needed. This is by 
far the hardest part of pretty-printing; naive approaches are 
susceptible to combinatorial explosion.