#+TITLE: :lang haskell

This module adds [[https://www.haskell.org/][Haskell]] support, powered by either [[https://haskell-lang.org/intero][intero]] (the default) or [[https://github.com/jyp/dante][dante]].

+ Code completion (~company-ghc~)
+ Look up documentation (~hoogle~)
+ eldoc support (~dante~)
+ REPL (~ghci~)
+ Syntax-checking (~flycheck~)
+ Code navigation (~dante~)
+ [[https://github.com/hlissner/emacs-snippets/tree/master/haskell-mode][Snippets]]

#+begin_quote
Haskell contends with C and Ruby as my favorite language. My Haskell code will never save the world, but I'll reach for it for small projects and programming exercises (like projecteuler.com or exercism.io).

I'd love to incorporate it into my machine learning work, but Python and Julia hold that crown. For now.
#+end_quote

* Table of Contents :TOC:
- [[#install][Install]]
  - [[#intero][Intero]]
  - [[#dante][Dante]]
- [[#troubleshooting][Troubleshooting]]
- [[#resources][Resources]]

* Install
This module has two submodules: *Intero* or *Dante*. To activate one, specify one or the other in your pubilc ~init.el~, e.g.:

#+BEGIN_SRC emacs-lisp
(doom! :lang (haskell +intero))
;; or
(doom! :lang (haskell +dante))
#+END_SRC

Your dependencies will change slightly, depending on which you choose:

** Intero
*** Haskell
To get started you must install *stack*:

**** MacOS
#+BEGIN_SRC sh :tangle (if (doom-system-os 'macos) "yes")
brew install haskell-stack
stack setup
#+END_SRC

**** Arch Linux
#+BEGIN_SRC sh :dir /sudo:: :tangle (if (doom-system-os 'arch) "yes")
sudo pacman --needed --noconfirm -S stack
# Replace pacaur with your AUR package manager of choice
pacaur --needed --noconfirm -S ncurses5-compat-lib
stack setup
#+END_SRC

*** External dependencies
This module requires ~ghc-mod~.

#+BEGIN_SRC sh
stack install ghc-mod
#+END_SRC

Also ensure that ~\~/.local/bin~ is in ~PATH~:

#+BEGIN_SRC sh
# place this in your profile file, like ~/.bash_profile or ~/.zshenv
export PATH="~/.local/bin:$PATH"
#+END_SRC

** Dante
*** Haskell
To get started with Dante and Haskell, you must install cabal

+ cabal (the haskell package builder)
+ ghc/ghci (the compiler, syntax checker & repl)

**** MacOS
#+BEGIN_SRC sh
brew install cabal-install ghc
#+END_SRC

**** Arch Linux
#+BEGIN_SRC sh
sudo pacman --needed --noconfirm -S cabal-install ghc
#+END_SRC

*** External dependencies
Dante requires ~ghc-mod~ and ~hoogle~:

#+BEGIN_SRC sh
cabal update
cabal install happy haskell-src-exts   # ghc-mod/hoogle dependencies
cabal ghc-mod hoogle
#+END_SRC

And add Cabal's bin path to $PATH:

#+BEGIN_SRC sh
export PATH="$HOME/.cabal/bin:$PATH"
#+END_SRC

* Troubleshooting
+ Stack users: a ~dist/setup-config~ in your project may cause [[ https://github.com/DanielG/ghc-mod/wiki#known-issues-related-to-stack][ghc-mod to not
  work]].

* Resources
Here are a few resources I've found indespensible in my Haskell adventures:

+ [[http://learnyouahaskell.com/][Learn you a haskell for great good]]
+ [[http://haskellbook.com/][Haskell Programming from first principles]]
+ [[https://github.com/krispo/awesome-haskell][Awesome Haskell]]: an extensive list of haskell resources
+ [[https://docs.haskellstack.org/en/stable/README/][The Haskell Tool Stack docs]]