add support for forth code blocks

  Currently only session code block evaluation is supported, however
  this is a reasonable default for forth.

* lisp/org.el (org-babel-load-languages): Add "Forth" to the list of
  loadable languages.

* list/ob-forth.el: New file.

lisp/ob-forth.el

@@ -0,0 +1,74 @@
+;;; ob-forth.el --- org-babel functions for Forth
+
+;; Copyright (C) 2014 Free Software Foundation, Inc.
+
+;; Author: Eric Schulte
+;; Keywords: literate programming, reproducible research, forth
+;; Homepage: http://orgmode.org
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Requires the gforth forth compiler and `forth-mode' (see below).
+;; https://www.gnu.org/software/gforth/
+
+;;; Requirements:
+
+;; Session evaluation requires the gforth forth compiler as well as
+;; `forth-mode' which is distributed with gforth (in gforth.el).
+
+;;; Code:
+(require 'ob)
+
+(defvar org-babel-default-header-args:forth '((:session . "yes"))
+  "Default header arguments for forth code blocks.")
+
+(defun org-babel-execute:forth (body params)
+  "Execute a block of Forth code with org-babel.
+This function is called by `org-babel-execute-src-block'"
+  (if (string= "none" (cdr (assoc :session params)))
+      (error "Non-session evaluation not supported for Forth code blocks")
+    (let ((all-results (org-babel-forth-session-execute body params)))
+      (if (member "output" (cdr (assoc :result-params params)))
+	  (mapconcat #'identity all-results "\n")
+	(car (last all-results))))))
+
+(defun org-babel-forth-session-execute (body params)
+  (require 'forth-mode)
+  (let ((proc (forth-proc))
+	(forth-rx (concat " " (regexp-opt (list "ok" "compiled")) "\n"))
+	(result-start))
+    (with-current-buffer (process-buffer (forth-proc))
+      (mapcar (lambda (line)
+		(setq result-start (progn (goto-char (process-mark proc))
+					  (point)))
+		(comint-send-string proc (concat line "\n"))
+		;; wait for forth to say "ok"
+		(while (not (progn (goto-char result-start)
+				   (re-search-forward forth-rx nil t)))
+		  (accept-process-output proc 0.01))
+		(unless (string= "compiled" (match-string 1))
+		  (buffer-substring (+ result-start 1 (length line))
+				    (match-beginning 0))))
+	      (split-string (org-babel-trim
+			     (org-babel-expand-body:generic
+			      body params))
+			    "\n" 'omit-nulls)))))
+
+(provide 'ob-forth)
+
+;;; ob-forth.el ends here

lisp/org.el

@@ -268,6 +268,7 @@ requirements) is loaded."
 		 (const :tag "Ditaa" ditaa)
 		 (const :tag "Dot" dot)
 		 (const :tag "Emacs Lisp" emacs-lisp)
+		 (const :tag "Forth" forth)
 		 (const :tag "Fortran" fortran)
 		 (const :tag "Gnuplot" gnuplot)
 		 (const :tag "Haskell" haskell)