Version 14 (modified by jstolarek, 3 years ago) (diff)


Emacs tips and tricks

Most of us use Emacs for GHC development. This page lists various Emacs configuration tips and tricks used by GHC developers. It is meant to be self-contained, so that you can grab relevant piece of configuration, put it into your config file and benefit from it instantly. The only exception are two larger extensions for Emacs (haskell-mode and ghc-mod), where we direct you to external installation instructions and tutorials.

Each entry includes a short description and instruction how to enable given setting (if it contains only a block of lisp code it means you need to add it to your .emacs configuration file). All configuration is given for Emacs 24, unless otherwise noted.

It is assumed that you know how to install packages in Emacs (e.g. with ELPA). TODO Let's not assume it. Can we create a saction "Installing extensions with ELPA" and give a short introduction on using it? I admit I don't remember how to use ELPA and would have to google it - JS.


IDO mode

Description: IDO stands for Interactively Do Things and it greatly improves file opening and switching between buffers. When opening a file it shows the list of files and directories in a current directory, allows to navigate the directory tree in an easy manner, provides intuitive filtering capabilities and allows to select a file by selecting its name using arrow keys. Similar behaviour is provided when switching between opened buffers. A nice introductory tutorial to IDO can be found here.

How to enable:

(setq ido-enable-flex-matching t)
(setq ido-everywhere t)
(ido-mode 1)

Disable tabs for indentation

Description: We used to use tabs for indentation, but now we aim to have no tabs in the source code. There is a hook that will prevent you from pushing tabs into repository (unless file already contained tabs). This setting will prevent you from introducing tabs in the source code.

How to enable:

(setq-default indent-tabs-mode nil)

Highlight text beyond 80th column

Description: If you have a tendency to write too long lines of code this will help you by highlighting text beyond 80th column.

How to enable:

(require 'whitespace)
(setq whitespace-style '(face lines-tail))
(setq whitespace-line-column 80)
(global-whitespace-mode t)

Automatically removes trailing whitespaces when file is saved

Description: Currently source code of GHC contains lots of trailing whitespaces, which means that this setting is dangerous. It will remove ALL trailing whitespaces in every file that you edit, which means you might have one or two lines changed by you and a hundred lines automatically changed by removing trailing whitespaces. This will require you to separate whitespaces into a separate commit by using git add -i. This is tedious, so be warned.

How to enable:

(add-hook 'before-save-hook 'delete-trailing-whitespace)

TODO describe how to enable this setting only if the file was already free of trailing-whitespaces at load-time

Highlight trailing whitespaces

Description: Automatic removal of trailing whitespaces described above can be a bit inconvenient to use. One of the alternative approaches to problem of trailing whitespaces is making them visible, so that you notice when you accidentally introduce them into a file. You will also see already existing trailing whitespaces. For more details see Useless Whitespace section of Emacs documentation.

How to enable:

(setq-default show-trailing-whitespace t)
(setq-default indicate-empty-lines t)

C-k kills whole line and newline if at beginning of line

Description: Allows to avoid typing C-k twice when cursor is placed at the beginning of a line.

How to enable:

(setq kill-whole-line t)

Toggle line number display

Description: Allows you to toggle line number display with F11. For those who like to see line numbers at the beginning of each line.

How to enable:

(global-set-key (kbd "<f11>") 'global-linum-mode)

Always display column number in mode line

Description: By default Emacs only displays line number in the mode line. This setting adds column number.

How to enable:

(column-number-mode 1)

Switch between windows with Alt-<window number>

Description: Enhances switching between multiple windows. Number of each windows is displayed in the mode line.

How to enable: You need to install package window-number and add this to your configuration:

(require 'window-number)

Cycle buffer

Will add this later


Haskell mode

Description: Haskell mode is a major mode for Emacs. Major features include syntax highlighting, GHCi integration and automatic indentation.

How to enable: See installation instructions on github and manual.


Description: I'm not using this one. Can someone (Kazu?) complete this section?

How to enable: See installation instructions here



Richard mentioned some interesting config on Newcomers page