* haskell-ts-mode

A haskell mode that uses treesitter.

* Screenshot

[[./ss.png]]

* Usage

=C-c C-r= to open REPL

=C-c C-c= to send code to repl

* Features

an overview of the features are:

- Syntax highliting

- Indentation

- Imenu support

- REPL (C-c r in the mode to run)

- Prettify symbols mode support

* Comparasion with haskell-mode

The more interesting features are:

- Logical syntax highlighting:

  - Only arguments that can be used in functions are highlighted, eg

    variable that is captured that can be used in body of function

  - The return type of a function is highlighted

  - All new variabels are(or should be) highlighted, this includes

    generators, lambda args.

  - highlighting the '=' operaotr in guarded matches correctly, this

    would be stupidly hard in regexp based syntax

- More perfomant, this is especially seen in longer files

- Much much less code, haskell mode has accumlated 30,000 lines of

  features to do with all things haskell related, this mode just keeps

  the scope to basic major mode stuff, and leaves other stuff for

  external packages.

* Motivation

about 30 years old.  Therefore, a lot of stuff emacs has gained the

ability to do in those years, haskell-mode already has implemented

them.

these problems. However because of haskell's syntax, it too became

very complex and required a web of dependencies.

Both these modes ended up practically parsing haskells syntax to

implement indentation, so I thought why not use tree sitter?

* Installation

The package is avaiable on elpa, you can install it using:

M-x package-install RET haskell-ts-mode RET

#+begin_src elisp

(add-to-list 'load-path "path/to/haskell-ts-mode")

(require 'haskell-ts-mode)

#+end_src

* Customization

If colour is too much or too less for you, adjust

If you want to highlight signature declarations (disabled by default),

add the following to your init file:

#+begin_src emacs-lisp

(setq haskell-ts-highlight-signature t)

#+end_src

** how to disable haskell-ts-mode indentation

#+begin_src emacs-lisp

(setq haskell-ts-use-indent nil)

#+end_src

** Pretify symbols mode

unicode alternatives.

#+begin_src emacs-lisp

(add-hook 'haskell-ts-mode 'prettify-symbols-mode)

#+end_src

** Adjusting font lock level

** Language server

#+begin_src emacs-lisp

#+end_src

- Imenu support for functions with multiple definitions