Haskell pretty printer
$ stack install hindent
$ hindent --help hindent --version --help --style STYLE --line-length <...> --indent-size <...> --no-force-newline [-X<...>]* [<FILENAME>] Version 5.1.1 Default --indent-size is 2. Specify --indent-size 4 if you prefer that. -X to pass extensions e.g. -XMagicHash etc. The --style option is now ignored, but preserved for backwards-compatibility. Johan Tibell is the default and only style.
hindent is used in a pipeline style
$ cat path/to/sourcefile.hs | hindent
The default indentation size is
2 spaces. Configure indentation size with
$ echo 'example = case x of Just p -> foo bar' | hindent --indent-size 2; echo example = case x of Just p -> foo bar $ echo 'example = case x of Just p -> foo bar' | hindent --indent-size 4; echo example = case x of Just p -> foo bar
.hindent.yaml file in your project directory or in your
~/ home directory. The following fields are accepted and are the
indent-size: 2 line-length: 80 force-trailing-newline: true
By default, HIndent preserves the newline or lack of newline in your input. With
force-trailing-newline, it will make sure there is always a trailing newline.
It is also possible to specify which extensions HIndent runs
with in your
extensions: - MagicHash - RecursiveDo
hindent-mode, which provides keybindings to reindent parts of the
M-qreformats the current declaration. When inside a comment, it fills the current paragraph instead, like the standard
C-M-\reformats the current region.
To enable it, add the following to your init file:
(add-to-list 'load-path "/path/to/hindent/elisp") (require 'hindent) (add-hook 'haskell-mode-hook #'hindent-mode)
'formatprg' option lets you use an external program (like
hindent) to format your text. Put the following line into
~/.vim/ftplugin/haskell.vim to set this option for Haskell files:
Then you can format with hindent using
:help gq and
help 'formatprg' for more details.
Note that unlike in emacs you have to take care of selecting a sensible buffer region as input to hindent yourself. If that is too much trouble you can try vim-textobj-haskell which provides a text object for top level bindings.
In order to format an entire source file execute:
Alternatively you could use the vim-hindent plugin which runs hindent automatically when a Haskell file is saved.
Fortunately, you can use https://atom.io/packages/ide-haskell with the path to hindent specified instead of that to stylish-haskell. Works like a charm that way!
IntelliJ / other JetBrains IDEs
- Install the "HaskForce" Haskell plugin (this is so we get the language type recognized in the file watcher)
- Install the "File Watchers" plugin under "Browse Repositories"
- Add a File Watcher with
- File type: Haskell Language
- Immediate file synchronization: off
- Show console: Error
Now whenever you save a file,
hindent should autoformat it.