Emacs for Programming Languages course on Coursera

Follow this guide: Swapping Capslock and Control keys

Put this in your shell init file (.bashrc, .zshrc…):

/usr/bin/setxkbmap -option "ctrl:swapcaps"

If you use Ubuntu, follow this guide: Swap caps lock and ctrl in ubuntu 13.10.

Follow this answer on StackOverflow: Emacs on Mac OS X Leopard key bindings

You can use your palm to press Control in standard PC keyboard.

These key bindings are also used by popular shells such as bash or zsh. I highly recommended you to master these key bindings.

• Move forward one char: C-f (f stands for forward)
• Move backward one char: C-b (b stands for backward)
• Move upward one line: C-p (p stands for previous)
• Move downward one line: C-n (n stands for next)

The above operations can also be done with arrow keys. if you don't like the above key bindings, the arrow keys offers equivalent features.

• Move to beginning of line: C-a
• Move to end of line: C-e
• Move forward one word, M-f.
• Move backward one word, M-b.

These key bindings are in Emacs only:

• Scroll forward one screen: C-v, page down
• Scroll backward one screen: M-v, page up
• Move to the beginning of a sentence: M-a
• Move to the end of a sentence: M-e
• Recenter a screen: M-l
• Re-position cursor to the top, middle and bottom of the current screen: M-r
• Move to top of the buffer: M-<
• Move to end of the buffer: M->
• Move to the nth character: M-g c (c stands for character)
• Move to the nth line: M-g l for Emacs < 23.2, M-g g for emacs >= 23.2) (l/g stands for line)

Recenter means making the current line the cursor is on the center of your screen.

You can quickly highlight a region by pressing C-SPC and use motion commands to select a region.

Exercise: execute the above commands using the key bindings at least 10 times or until you remember. You can perform these motion commands on any buffer.

So, you want to look for something in the buffer? C-s invokes isearch-forward, allows you to look forward from the current point for something. After C-s, you are prompted to enter the content to search for. Enter the content, and press C-s repeatedly to travel through the matches forward.

Similarly, C-r invokes isearch-backward, allows you to look backward from the current point. Press C-r repeatedly to travel through the matches backward.

isearch can be invoked from any valid buffer.

In Emacs, kill means Cut in other editors. These key bindings also work under the terminal.

• Kill a character at the cursor: C-d
• Kill entire line: C-S-DEL (remember, DEL is your <backspace> key), or C-w (not in stock Emacs)
• Kill forward to the end of a word from current cursor: M-d
• Kill backward to the beginning of a word from the current cursor: M-DEL
• Kill all spaces at cursor: M-\
• Kill all spaces except one at cursor: M-SPC
• Kill to the end of line: C-k
• Kill a sentence: M-k
• Undo: C-/
• Redo: C-?
• Open a list of killed texts: M-y (not in stock Emacs)
• Duplicate line/region: M-c (not in stock Emacs)
• Indent whole buffer: C-c i (not in stock Emacs)

When you kill something, the killed content is put into the Kill Ring.

If you write code, you can also quickly add comments or comment/uncomment code with M-;:

• If you do not highlight a text region, M-; adds a comment to the end of line.
• If you do not highlight a text region and comment is at the end of line, M-; comments the whole line (not in stock Emacs).
• If you do not highlight a text region and your current line is being commented, M-; uncomments the whole line (not in stock Emacs).
• If you highlight a region (i.e. with a mouse), M-; comments out the region.

Buffer is where you edit your file content. Buffer holds content of a file temporarily. Anything you write into the buffer won't make it into file until you explicitly save it with save-buffer command. C-x C-s executes the command save-buffer, so you can C-x C-s your files. You can also execute this from M-x*

To save a buffer as other file ("Save As" in other editors), C-x C-w, which runs the commands write-file.

To kill a buffer, C-x k. If you want to kill the current buffer, RET immediately. Otherwise, type into the prompt the buffer name you want to kill.

In the above section, I said that point is in your file, well, actually point is not in a file but a buffer. From now on, keep file and buffer two separate and distinct concepts. When I say file, I refer to physical file and when I say buffer, I refer to the temporary content of the file that is being displayed.

Exercise: Practice C-x b to get used to it.

Unlike other editors, Emacs can split your frame area into multiple smaller areas. Each such area is called a window. You can divide a frame into as many windows as you want and each window can have anything in it, i.e. your current editing buffer, file management buffer, help buffer, a shell… Basically anything that Emacs can display. Let's try them out:

Exercise:

C-x 2 to split the current window into two horizontal windows. After splitting, you will have the exact duplicate of your current editing buffer. split-window-below is bound to C-x 2.

C-x 3 to split your current window into two vertical windows. After splitting, you will have the exact duplicate of your current editing buffer. split-window-right is bound to C-x 3.

Now, after you execute the two commands above, you will have three windows: two above and one below. Each window can hold a buffer. With the above two commands ,you can create arbitrary window layout. In Emacs, a window layout is called a window configuration.

To navigate through the windows, use C-x o which runs the command other-window. Try cycling around the windows a few times to get used to it.

In Emacs, <next> is the PageDown key, <prior> is the PageUp key. M-<next> runs scroll-other-window and scroll the other window forward; M-<prior> runs scroll-other-window-down and scroll the other window backward. Other window is the window that you visit when C-x o.

C-x 0 closes the window at point.

C-x 1 closes all other windows except the currently selected one. Try creating another window, try C-x 1. Only in my distribution: C-x 1 again opens previous window layout.

• aggressive-indent is a minor mode that keeps your code always indented. It reindents after every command. It is available for Lisp modes (such as Racket, Common Lisp, Emacs Lisp…) in this distribution for the course.

  

• You can also run C-c i to indents whole buffer. In Lisp modes, you won't need it; but for other programming modes, C-c i is always useful.

comment-dwim2 is a package that provides extended features compare with the original command comment-dwim. dwim stands for do what i mean; it means that the commands with dwim suffix changes it behaviors based on context at point. For example, comment-dwim2 comments line at point if it is uncommented; execute again uncomments the line and put a comment at end of line; execute again comments the whole line; execute again uncomment the line and returns to original state and we repeat the whole process again. These behaviors work on region as well.

You can click the link to the homepage to see the demos.

From the homepage:

Geiser is a collection of Emacs major and minor modes that conspire with one or more Scheme interpreters to keep the Lisp Machine Spirit alive. It draws inspiration (and a bit more) from environments such as Common Lisp’s Slime, Factor’s FUEL, Squeak or Emacs itself, and does its best to make Scheme hacking inside Emacs (even more) fun.

When working with a fully conniving Scheme, Geiser can offer the following functionality:

• Form evaluation in the context of the current file’s module.
• Macro expansion.
• File/module loading and/or compilation.
• Namespace-aware identifier completion (including local bindings, names visible in the current module, and module names).
• Autodoc: the echo area shows information about the signature of the procedure/macro around point automatically.
• Jump to definition of identifier at point.
• Access to documentation (including docstrings when the implementation provides it).
• Listings of identifiers exported by a given module.
• Listings of callers/callees of procedures (only available in Guile Scheme).
• Rudimentary support for debugging (when the REPL provides a debugger) and error navigation.
• Support for multiple, simultaneous REPLs.
• Support for image display in those Schemes that treat them as first class values.

This tutorial only offers a subset of these features, enough to mkae you comfortable with the course.

• Split your Emacs in two windows: one for source code, one for REPL
• Write some code in source buffer.
• Evaluate whole buffer and switch to the context of that buffer with C-c C-a. When you write a Racket file, you are writing a module. To use definitions in the module, you have to switch to that module. C-c C-a automatically evaluates the file of current working buffer and switch context to that module. Note that if you haven't save your buffer, Geiser will use the last saved state. You can also use C-c C-b to execute current file without switching to the REPL. This is useful when you want to write and run test continuously, i.e. write a few tests then execute, then write a few more and test a few more etc…
• Play with your code in the REPL and see the result instantly.

Demo (begins when START DEMO appears in minibuffer):

In this demo, I executed my test case with C-c C-a. The test were sequentially executed and the results were printed on the REPL. In case it Racket requires graphics, a Window is popped up as you can see in the dan-then-dog function test.

Geiser also provides common features found in IDE:

• Autodoc: The minibuffer shows information about the signature of the function/macro around point automatically. It is enabled by default when geiser-mode is activated.

  

• Code completion: Geiser uses Emacs's default completion-at-point command to provide completion candidates. By default, it is bound to C-M-i (the equivalent of M-TAB); in my Emacs configuration for this guide, I bound it to TAB for buffers with Geiser mode for convenience.
• Jump to definition: You can jump to any symbol at point in a Racket buffer while Geiser REPL is active with M-.. To go back to where you were, use M-,.

• Open documentation at point: For any symbol, you can execute C-c C-d C-d to open a buffer that has a brief summary of that symbol, along with two buttons for accessing either its actual source code: [source] button or its HTML documentation in an external browser: [manual] button.

  

• More evaluation commands: These commands works at expression level.

These are enough for the Racket part of the course. To learn more Geiser features, please refer to official documentation.