hamacs/ha-programming-scheme.org

Programming in Scheme for SICP

A literate programming file configuring Emacs.

Introduction

First, install MIT-Scheme, the Lisp dialect used throughout the SICP book: brew install mit-scheme or sudo apt install mit-scheme .

  brew install mit-scheme

Or better yet, let’s use Guile:

  brew install guile

Geiser (Scheme Interface)

The geiser project attempts to be the interface between Emacs and all the Schemes in the world. Since I can’t decide which to use, I’ll install/configure them all.

  (use-package geiser
    :init
    (setq geiser-mit-binary "/usr/local/bin/scheme"
          geiser-racket-binary "/usr/local/bin/racket"
          geiser-guile-binary "/usr/local/bin/guile"
          geiser-active-implementations '(guile mit)
          geiser-default-implementations '(guile))
    :config
    (use-package geiser-mit)
    (use-package geiser-guile)
    (use-package geiser-racket))

Org Mode

Do we need a Scheme work for Org Babel? According to this document, we just need to make sure we add the :session variable to start the REPL.

  (use-package ob-scheme
    :straight (:type built-in)
    :config
    (add-to-list 'org-babel-load-languages '(scheme . t)))

Since the version of Scheme hasn't been updated with the deprecation, and subsequent removal of org-babel-get-header, we include it here:

  (defun org-babel-get-header (params key &optional others)
    (delq nil
          (mapcar
           (lambda (p) (when (funcall (if others #'not #'identity) (eq (car p) key)) p))
           params)))

Let’s test it out by defining a variable:

  (define a 42)

And simply using it:

  (+ a b)

;Value: 50

And what about Scheme-specific stuff needed for SICP?

  (inc 42)

Install SICP

Let’s get the book available as an Info page:

(use-package sicp)

Still having difficulty getting the Scheme REPL to output the results back into this document. Let’s try Racket…

Normally, I would just read the book, however, if we want to read the sicp.info file, we need this, at least, temporarily:

(add-to-list 'auto-mode-alist '("\\.info\\'" . Info-mode))

Racket

Actually, let’s do this with Racket:

  brew install racket

While Racket, as a Scheme, should work with Geiser (below), let’s also get racket-mode working:

  (use-package racket-mode
    :config (setq racket-program "/usr/local/bin/racket"))

Can we get Racket working with Org?

  (use-package ob-racket
    :straight (:host github :repo "DEADB17/ob-racket")
    :after org
    :config
    (add-to-list 'org-babel-load-languages '(racket . t)))

Try It Out

Working for values?

  (* 6 7)

42

Working for output?

  (define str-1 "hello")
  (define str-2 "world")
  (define all (string-join (list str-1 str-2) ", "))
  (display (string-titlecase all))

Hello, World

The interface is horrendously slow, as the :session doesn’t seem to work, and starting up a Racket REPL takes a long time.

SICP and Racket

If using Racket for SICP, install the SICP language:

  raco pkg install --auto --update-deps sicp

We now can give it a #lang sicp (or better yet, use the :lang header) to define certain SICP-specify features:

Let’s try this now:

(inc 42)

43