spacemacs/contrib/lang/haskell

Haskell contribution layer for Spacemacs

Table of Contents

• Haskell contribution layer for Spacemacs
  • Description
  • Install
    • Layer
    • Cabal packages
    • OS X
    • Optional extras
      • GHCi-ng support
      • structured-haskell-mode
      • hindent
  • Key bindings
    • Haskell source code:
      • Haskell commands:
      • Documentation commands:
      • Cabal commands:
      • Debug commands:
      • REPL commands:
    • Cabal files:

Description

This layer adds support for the Haskell language.

Features:

• auto-completion with company-ghc,
• auto-indentation with hi2.

This layer is in construction, it needs your contributions and bug reports.

Install

Layer

To use this contribution add it to your ~/.spacemacs

(setq-default dotspacemacs-configuration-layers '(haskell))

Cabal packages

This layer requires some cabal packages:

• ghc-mod
• hlint
• stylish-haskell

To install them, use the following command:

cabal install stylish-haskell hlint ghc-mod

Next Emacs needs to know where to find these binaries, you can locate them with the following shell command:

dirname $(which ghc-mod)

Then you have to add this path to your system $PATH (preferred):

export PATH=~/.cabal/bin/:$PATH

or to the Emacs exec-path variable in the dotspacemacs/init function of your .spacemacs file:

(add-to-list 'exec-path "~/.cabal/bin/")

Note: it is important to add the path in the dotspacemacs/init function, so that the path is added before any layers is loaded.

OS X

Note that emacs.app for OS X does not pick up $PATH from ~/.bashrc or ~/.zshrc when launched from outside a terminal.

Optional extras

The Haskell layer supports some extra features that can be enabled through layer variables.

GHCi-ng support

ghci-ng adds some nice features to haskell-mode, and is supported in Spacemacs by a layer variable:

Follow the instructions to install ghci-ng (remember to add :set +c in ~/.ghci, next set the layer variable:

;; List of configuration layers to load.
dotspacemacs-configuration-layers
'(company-mode
  git
  (haskell :variables haskell-enable-ghci-ng-support t))

Once ghci-ng is enabled, two of the old keybindings are overriden with improved versions from ghci-ng, and a new keybinding available:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m t | gets the type of the identifier under the cursor or for the active region SPC m g g | go to definition SPC m u | finds uses of identifier

structured-haskell-mode

structured-haskell-mode, or shm, replaces hi2 (and any other Haskell-indentation modes) and adds some nice functionality. To enable shm, run cabal install structured-haskell-mode and set the layer variable:

;; List of configuration layers to load.
dotspacemacs-configuration-layers '(company-mode (haskell :variables haskell-enable-shm-support t) git)

After shm has been enabled, some of the evil normal-mode bindings are overridden:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ D | shm/kill-line R | shm/raise P | shm/yank ( | shm/forward-node ) | shm/backward-node

For a nice visualization of these functions, please refer to the github page for structured-haskell-mode.

hindent

hindent is an extensible Haskell pretty printer, which let's you reformat your code. You need to install the executable with cabal install hindent; to enable it set:

;; List of configuration layers to load.
dotspacemacs-configuration-layers
  '(company-mode
    git
    (haskell :variables haskell-enable-hindent-support t))

By default it uses the style called fundamental, if you want to use another, johan-tibell, run M-x customize-variable hindent-style.

Key bindings

All Haskell specific bindings are prefixed with SPC m

Haskell source code:

Haskell commands:

Top-level commands are prefixed by SPC m:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m t | gets the type of the identifier under the cursor SPC m i | gets information for the identifier under the cursor SPC m g g | go to definition or tag SPC m f | format buffer using haskell-stylish SPC m F | format declaration using hindent (if enabled)

Documentation commands:

Documentation commands are prefixed by SPC m h

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m h d | find or generate Haddock documentation for the identifier under the cursor SPC m h h | do a Hoogle lookup SPC m h y | do a Hayoo lookup

Cabal commands:

Cabal commands are prefixed by SPC m c:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m c a | cabal actions SPC m c b | build the current cabal project, i.e. invoke cabal build SPC m c c | compile the current project, i.e. invoke ghc SPC m c v | visit the cabal file

Debug commands:

Debug commands are prefixed by SPC m d:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m d d | start debug process, needs to be run first SPC m d b | insert breakpoint at function SPC m d n | next breakpoint SPC m d N | previous breakpoint SPC m d B | delete breakpoint SPC m d c | continue current process SPC m d a | abandon current process SPC m d r | refresh process buffer

REPL commands:

REPL commands are prefixed by SPC m s:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m s b | load or reload the current buffer into the REPL SPC m s c | clear the REPL SPC m s s | show the REPL SPC m s S | show and switch to the REPL

Cabal files:

Key Binding       |                 Description

----------------------|------------------------------------------------------------ SPC m d | add a dependency to the project SPC m b | go to benchmark section SPC m e | go to executable section SPC m t | go to test-suite section SPC m m | go to exposed modules SPC m l | go to libary section SPC m n | go to next subsection SPC m p | go to previous subsection SPC m N | go to next section SPC m P | go to previous section SPC m f | find or create source-file under the cursor