jluningp / smlformat

An auto-formatter for the Standard ML language

SMLFormat

SMLFormat is an autoformatter for the Standard ML programing language. It indents, keeps lines under 80 characters, and applies a set of heuristics to prettify code.

The source code of SMLFormat is formatted with SMLFormat.

Installation

1. Install the SML/NJ compiler.
2. Clone this git repo: git clone https://github.com/jluningp/smlformat.git SMLFORMAT_DIR.
3. Add SMLFormat to your path (replacing SMLFORMAT_DIR with your SMLFormat directory):

$ echo "PATH=\"\$PATH:SMLFORMAT_DIR\"; export PATH" >> ~/.bashrc
$ source ~/.bashrc

4. Follow the instructions below for editor installation.

Usage

SMLFormat can read from stdin and write to stdout, or it can take files as arguments.

Usage: smlformat [-i inputfile] [-o outputfile]
  -i infile    read code from file instead of stdin
  -o outfile   write formatted code to file instead of stdout
  -h           print this help message

Examples

Read from file:

$ echo "fun foo x =     10" > test.sml
$ smlformat -i test.sml 
fun foo x = 10

Write to file:

$ echo "fun foo x =    10" | smlformat -o test_output.sml
$ cat test_output.sml
fun foo x = 10

Read and write files:

$ echo "fun foo x =     10" > test.sml
$ smlformat -i test.sml -o test_output.sml
$ cat test_output.sml
fun foo x = 10

Read from stdin and write to stdout:

$ echo "fun foo x =    10" | smlformat
fun foo x = 10

Format a file "in-place":

$ echo "fun foo x =     10" > test.sml
$ smlformat -i test.sml -o test.sml
$ cat test.sml 
fun foo x = 10

If an input fails to parse, SMLFormat cannot format it and will return the original input.

$ echo "val x" | smlformat 
val x

You can also manually run SMLFormat in the SML/NJ REPL by running

sml -m SMLFORMAT_DIR/sources.cm
- SmlFormat.format "input.sml";
val () = ()
-

Editors

Emacs

Setup

1. If you want to format on save, uncomment the bottom line of editors/emacs/smlformat.el.
2. Add the following line to your .emacs, with SMLFORMAT_DIR replaced by your SMLFormat directory:

(load "SMLFORMAT_DIR/editors/emacs/smlformat.el")

4. Reopen emacs

Usage

1. Save the file you're working on
2. M-x smlformat
3. If your file doesn't parse when you run SMLFormat, it will not be formatted.

Vim

Setup

1. Install the Neoformat vim plugin
2. Copy the files in editors/vim into Neoformat's formatters directory¹.

cp editors/vim/* ~/.vim/plugged/neoformat/autoload/neoformat/formatters/

3. To enable formatting on save, add the following to your .vimrc:

autocmd BufWritePre *.sml,*.sig Neoformat

¹ Why is there sml.vim and lprolog.vim? Vim thinks .sig files have filetype lprolog

Usage

1. : Neoformat
2. If your file doesn't parse when you run SMLFormat, it will not be formatted.

Known Issues

1. Types have too many parentheses around them
2. Functor signatures get deleted
3. Indentation with constructors + newlines is weird (maybe an extra indent?)