What’s this?

This post is a quick introduction on using Guile Scheme within Emacs, written mainly for future me. You’re welcome, future Rohan!

Why?

I tend to jump between languages a lot and my general-purpose editor of choice is Sublime Text. Lately, though, I’ve been programming in Guile Scheme for my Summer of Code project, which means I’ve been playing around in Emacs a lot. It’s fun and I really love the Emacs/Scheme workflow, but the only downside is that the shortcuts are a little different from those I’m used to in Sublime Text. Hence, this post. Although all this information is anyway available in the GNU Emacs guide and the Geiser guide, I’ve culled the unimportant stuff and condensed the useful bits into this blog post.

Quick Note

In the shortcuts that follow, C is Ctrl, M is Alt, RET is Enter and S is Shift. <mouse-11> is the left click mouse button, and <mouse-3> is the right click mouse button.

Starting out

Get Emacs 24 with apt-get install emacs24.

Then, theme it to your liking. This means creating a file named init.el and placing it in the ~/.emacs.d directory. Here are my settings, with comments explaining the configuration.

Once you’re done changing init.el, run M-x eval-buffer to tell Emacs about it - or just M-x eval-region to eval a particular sexp.

Next, install Geiser with M-x package-install RET geiser RET.

Basic Emacs stuff

• C-g cancels the minibuffer command.
• C-x C-s saves your work.
• C-x C-f visits a file (which means it opens it if it exists and creates it if it doesn’t).
• C-x 0 closes the current buffer.
• C-x 1 closes everything except the current buffer.
• C-x-2 splits the current buffer horizontally and duplicates it in the newly created window.
• C-x-3 does the same thing as above, except vertically.
• M-x man RET pagename RET opens up the man pages for pagename.
• C-h i opens the info pages. This includes the info pages for Emacs, Geiser, Guile and many other GNU programs and software.
• C-h k describes a keybinding. For example, try C-h k C-h k.
• C-x k buffername RET kills the buffer named ‘buffername’. Merely typing C-x k allows you to scroll up and down and select a buffer to be killed. Or you can type in the first few letters of the buffername and hit TAB to autocomplete.
• C-x b buffername RET visits the buffer named ‘buffername’. Its behaviour is similar to that of C-x k.
• M-; comments or uncomments a region, short for M-x comment-region.
• C-x l counts the number of lines in the page, and displays in brackets the number of lines before and after the cursor position.

Using Geiser

Note: Geiser supports Racket and Chicken Scheme too, but those aren’t relevant to us right now.

• M-x run-guile summons a Guile REPL.
• C-c C-z switches between the .scm file currently being edited and this REPL.
• C-up goes back in history at the Guile REPL.
• C-down goes forward in history at the Guile REPL.

Dealing with sexps

Moving around

• C-M-f (f = forward) jumps to the end of the sexp in front of the current edit point.
• C-M-b (b = backward) jumps to the beginning of the sexp behind the current edit point.
• C-M-S-f selects the sexp in front of the current edit point (Makes sense: Shift is used for selection).
• C-M-S-b: same thing, but for the sexp behind the current edit point.
• C-i intelligently indents the selected region. If no region is selected, it indents only the current line.

Guile and sexps

• C-x C-e evaluates the sexp behind the current edit point.
• C-c C-b evaluates the entire buffer.

Commenting

• Putting “*;” before a sexp comments it out (as well as all contained sexps), while leaving the containing sexps intact.

Buffers

• M-x buffer-menu brings up the list of active buffers. This is useful because sometimes Emacs decides to reuse a window carrying one of your useful buffers for something else, like showing error messages when Geiser evaluates an sexp, or showing minibuffer command completion candidates. Use up and down to move around the buffers list, and hit RET when you find the buffer you were looking for.
• If you just want to look at a buffer, but not interact with it, do M-x view-buffer RET and then navigate to the buffer you want.
• C-x o (o = other) switches between visible buffers.
• C-<mouse-1> brings up a graphical buffer menu.

Viewing RFCs

• For reading RFCs, I use irfc. Get it by following the instructions here.
• M-x irfc-visit RET 2131 downloads RFC 2131 (if it isn’t already download) to the location specified in init.el and opens it in the current buffer.