datum-comments

#+title: datum comments for common lisp

[[img:https://travis-ci.org/tgbugs/datum-comments.svg?branch=master][https://travis-ci.org/tgbugs/datum-comments]]

Racket style =#;= comments implemented as a dispatch macro.

#+begin_src lisp
#; ; regular comments are treated as whitespace
(and the next datum is skipped by the reader)
#; (so you can skip a datum inline) (print "and not just a line or block")
#+end_src

* Installation
** [[https://www.quicklisp.org/][Quicklisp]]
#+begin_src lisp
(ql:quickload :datum-comments)
#;(skip) '(show)  ; datum comments work immediately after quickload
#+end_src

** Manual install
Using =sbcl= as an example.
#+begin_src bash
git clone https://github.com/tgbugs/datum-comments.git
cat "(push (truename #p\"datum-comments\") asdf:*central-registry*)" >> ~/.sbclrc
sbcl --eval "(asdf:load-system :datum-comments) #;(i im a comment) (print 'hello)"
#+end_src

* Usage
Since comments are a fundamental part of a language datum-comments automatically
registers itself as a dispatch macro for the =#;= symbol. Install via one of the
methods above and then include =:datum-comments= in the =:use= section of
=defpackage= where you want to be able to use datum comments, e.g. as

#+begin_src lisp
(defpackage :my-package
  (:use :cl :datum-comments))
#+end_src

at which point you can =#;(use datum comments to your heart's content)=

* Implementation support
This should work on any cl that has =asdf=, and the copy/paste version
below should work on pretty much anything.
See [[https://travis-ci.org/tgbugs/datum-comments][travis]] for the list
of tested working implementations.

* Standalone
#+begin_src lisp
(defpackage :datum-comments
  (:use :cl))
(in-package :datum-comments)
(defun datum-comment (stream char arg)
  (declare (ignore char arg))
  (read-preserving-whitespace stream t nil t)
  (values))
(set-dispatch-macro-character #\# #\; #'datum-comment)
#+end_src

* Syntax highlighting and editing
An experimental [[./datum-comments.el][datum-comments-mode]] is available for emacs. A minimal
entry for [[${HOME}/.emacs][~/.emacs]]/[[${HOME}/.emacs.d/init.el][init.el]]
is below.
#+begin_src emacs-lisp :eval never
(use-package lisp-mode
  :init
  (use-package datum-comments
    :load-path "~/git/datum-comments" ;; adjust accordingly
    :hook (lisp-mode . datum-comments-mode)))
#+end_src

This will probably fail right now unless you also have slime enabled,
and has not been sufficiently tested.

Support for named readtables or detection by slime of a datum-comments
feature has not been implemented but is planned.

There are also known bugs with the interaction between regular comments
and datum comments causing datum comments to be highlighted incorrectly.
* Racket behavior for comparison
#+begin_src racket :results none
#lang racket/base
#;(this is commented out) '(this is not) ; this is
#;(this should break how does greg avoid the issue? ; this is a comment)
        and this is open ended)

#;
(test this should ;be ok right?)
      #; nothing)

;; double, the racket behavior is as expected, comments are comments
#; ; help I'm
#; ; trapped in
(one fish) ; yay!
(two fish) ; woo!

#; #; 'one 'two 'three
#+end_src


datum-comments

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datum-comments

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