Emacs is a Lisp. Clojure is a Lisp. Can the two be put together to form the ultimate dev environment? "Clomacs" perhaps?

• from Emacs isn't for everyone discussion by Anonymous Cow.

Clomacs simplifies call Clojure code from Emacs lisp and vice versa. The purpose is to provide a tool for creating mixed Elisp-Clojure Emacs extensions. It provides a small wrapper under CIDER to reduce repetitive code and uses simple-httpd to call Elisp from Clojure via http requests.

There are some requirements to run mixed Elisp-Clojure code. All the Elisp-side code should be loaded, nREPL must run with all related Clojure-side code and its dependencies.

So, the user of the mixed Elisp-Clojure Emacs extension wants to simple run Elisp code from the extension.

The purpose of the clomacs-defun is to wrap Clojure function in a Elisp function, that will start CIDER if necessary or use an existing CIDER connection of certain Elisp-Clojure Emacs extension, call this Clojure function and return it's result.

To run Elisp code from Clojure, http server on Emacs side should be started first by clomacs-httpd-start function. Then you can straightforwardly pass Elisp code as string to Emacs for eval - clomacs-eval or wrap Elisp to Clojure function via clomacs-defn.

Add MELPA (if not yet) to your package-archives list.

Then you can install clomacs with the following command:

M-x package-install [RET] clomacs [RET]

To install Clomacs, add the following dependency to your project.clj file:

clomacs requires Clojure 1.7+.

Call Clojure from Elisp:

;; emacs lisp:
(require 'clomacs)
(clomacs-defun get-property System/getProperty)
(message (get-property "java.version"))

Call Elisp from Clojure:

;; emacs lisp:
(require 'clomacs)
(clomacs-httpd-start)

;; clojure:
(use 'clomacs)
(clomacs-defn emacs-version emacs-version)
(println (emacs-version))

Here System/getProperty is a Clojure function and get-property is a wrapped Elisp function. emacs-version is Elisp function and after macros evaluation - is a wrapped Clojure function.

The full source code for the following example is here: cm-test.

1. Create new Clojure project in a common way:

lein new cm-test

2. Add markdown-clj dependency to the project.clj file, add src/clj folder to the classpath:

(defproject cm-test "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :source-paths ["src/clj"]                    ;; add clj folder to the classpath
  :dependencies [[org.clojure/clojure "1.9.0"] ;; Use recent version of Clojure
                 [markdown-clj "0.9.28"]       ;; markdown-clj dependency
                 [clomacs "0.0.3-SNAPSHOT"]])  ;; Most recent version of clomacs

3. Create clj folder in the src/.
4. Copy cm_test to src/clj/ folder.
5. Add some code, using markdown lib in the src/clj/cm_test/core.clj file:

(ns cm-test.core
  (:use markdown.core))

(defn my-md-to-html-string
  "Call some function from the dependency."
  [x]
  (md-to-html-string x))

6. Create elisp folder in the src/.
7. Create cm-test.el file in this foder.
8. Add to the cm-test.el the following content:

(require 'clomacs)
(clomacs-defun cm-test-md-to-html-wrapper
               cm-test.core/my-md-to-html-string
               :lib-name "cm-test"
               :namespace cm-test.core
               :doc "Convert markdown to html via Clojure lib.")

(defun cm-test-mdarkdown-to-html (beg end)
  "Add to the selected markdown text it's html representation."
  (interactive "r")
  (save-excursion
    (if (< (point) (mark))
        (exchange-point-and-mark))
    (insert
     (concat "\n" (cm-test-md-to-html-wrapper
                   (buffer-substring beg end))))))

(provide 'cm-test)

Here is the cm-test/src path tree vizualization:

• src
  • clj
    • cm_test
      • core.clj
  • elisp
    • cm-test.el

9. So, it can be used in your .emacs via:

(add-to-list 'load-path "~/.emacs.d/cm-test/src/elisp/")
(require 'cm-test)

10. Then mark (select) this text in one of your buffers:
# This is a test
and run M-x cm-test-mdarkdown-to-html.

<h1>This is a test</h1> should occurs in the buffer under the original text.

• cm-test - Clomacs usage example.
• ejc-sql - Emacs SQL client uses Clojure JDBC.
• flower - Integration with Github, Gitlab, Atlassian Jira, Microsoft TFS, Microsoft Exchange and Slack.

• GNU Emacs 26.3+.
• CIDER
• s.el
• simple-httpd

Copyright © 2013-2020 Kostafey kostafey@gmail.com and contributors

Distributed under the General Public License, version 3.