#+TITLE: Programming Haskell
#+AUTHOR: Howard X. Abrams
#+DATE:   2022-08-24
#+FILETAGS: :emacs:

A literate programming file for configuring Emacs to use [[https://www.haskell.org/][Haskell]] .
#+begin_src emacs-lisp :exports none
  ;;; ha-programming-haskell --- configuring for haskell. -*- lexical-binding: t; -*-
  ;;
  ;; © 2022-2023 Howard X. Abrams
  ;;   Licensed under a Creative Commons Attribution 4.0 International License.
  ;;   See http://creativecommons.org/licenses/by/4.0/
  ;;
  ;; Author: Howard X. Abrams <http://gitlab.com/howardabrams>
  ;; Maintainer: Howard X. Abrams
  ;; Created: August 24, 2022
  ;;
  ;; While obvious, GNU Emacs does not include this file or project.
  ;;
  ;; *NB:* Do not edit this file. Instead, edit the original literate file at:
  ;;            ~/other/hamacs/ha-programming-haskell.org
  ;;       And tangle the file to recreate this one.
  ;;
  ;;; Code:
  #+end_src
* Introduction
While “they” claim a [[https://www.haskell.org/tutorial/][Gentle Introduction]], it doesn’t look /fun/. I bought the book, [[http://learnyouahaskell.com/chapters][Learn You a Haskell for Great Good!]], which looks better. Before an /Emacsian/ can dive into a new language, one needs to get an Emacs environment working.

First, get it installed. On a Mac, do something like:
#+begin_src sh
  brew install haskell-stack
#+end_src
Which installs the [[https://docs.haskellstack.org/][Haskell Stack]] project that is basically an interface to the /kitchen sink/.

And then run:
#+begin_src sh
  stack setup
#+end_src

And then you get access to an interactive session in a virtual environment with:
#+begin_src sh
  stack ghci
#+end_src
* Haskell Mode
Seems that the venerable [[https://github.com/haskell/haskell-mode][haskell-mode]] is the best.
#+begin_src emacs-lisp
  (use-package haskell-mode
    :custom
    (haskell-process-type 'stack-ghci))
#+end_src

See [[https://input-output-hk.github.io/adrestia/resources/Emacs][this configuration]] for some advanced features.

The [[https://github.com/mihaimaruseac/hindent][hindent package]] looks interesting:
#+begin_src emacs-lisp
  (use-package hindent
    :custom (hindent-style "johan-tibell")
    :hook (haskell-mode . #'hindent-mode))
#+end_src
* Haskell and Org
#+begin_src emacs-lisp
  (use-package ob-haskell
    :straight (:type built-in)
    :config
    (add-to-list 'org-babel-load-languages '(haskell . t)))
#+end_src

And let’s see if this works:
#+begin_src haskell :results replace value
  nums = filter (> 2) [1 .. 5]
  zip nums ['a' .. 'e']
#+end_src

#+RESULTS:
| 3 | a |
| 4 | b |
| 5 | c |

* Technical Artifacts                                :noexport:
Let's =provide= a name so we can =require= this file:
#+begin_src emacs-lisp :exports none
  (provide 'ha-programming-haskell)
  ;;; ha-programming-haskell.el ends here
  #+end_src

#+DESCRIPTION: configuring Emacs.

#+PROPERTY:    header-args:sh :tangle no
#+PROPERTY:    header-args:emacs-lisp  :tangle ~/.emacs.d/elisp/ha-programming-haskell.el
#+PROPERTY:    header-args    :results none :eval no-export :comments no mkdirp yes

#+OPTIONS:     num:nil toc:nil todo:nil tasks:nil tags:nil date:nil
#+OPTIONS:     skip:nil author:nil email:nil creator:nil timestamp:nil
#+INFOJS_OPT:  view:nil toc:nil ltoc:t mouse:underline buttons:0 path:http://orgmode.org/org-info.js