Forth Code Blocks in Babel

Forth is a stack-based language that is able to extend itself during runtime. It is an interactive language with interactive compilation, during which the parser is visible to the programmer.

This Forth tutorial intends "that you work through it while sitting in front of the console, take a look at the examples and predict what they will do, then try them out; if the outcome is not as expected, find out why (e.g., by trying out variations of the example), so you understand what's going on."

Babel support for Forth code blocks requires a working installation of the gforth compiler. Other Forth Systems are not supported by Babel.

The gforth compiler is distributed with the file gforth.el, which provides forth-mode, the official Emacs programming language mode for Forth. Note that Babel does not support other implementations of forth-mode, such as this implementation distributed via MELPA.

To configure Forth code blocks in Org mode, add the appropriate dotted pair to org-babel-load-languages:

(org-babel-do-load-languages
 'org-babel-load-languages
 '((forth . t))) ; this line activates Forth

Babel evaluates Forth code blocks in an inferior Forth process, which must be running when the code block is evaluated. You can start an inferior Forth process with M-x run-forth.

Babel supports Forth sessions, which run in a buffer named *forth* by default. Non-session evaluation is not supported by Babel, so :session none raises an error. Any other value assigned to :session is ignored.

There are no Forth-specific header arguments.

Here is the obligatory Hello World! example in Forth.

#+begin_src forth 
." Hello World!"
#+end_src

#+RESULTS:
: Hello World!