1 unstable release

0.1.0 Jul 23, 2023

#2106 in Command line utilities

MIT license

19KB
488 lines

sexpfmt

S-expressions are easy for machines to write, but generating formatted S-expressions can be painful. sexpfmt formats an input stream in a consistent way such that the output is both line-diffable and human-readable.

The formatting style used by sexpfmt is highly regular, unlike what many Lispers and Schemers prefer. Each indentation increments spaces by a fixed number of spaces (by default, 2).

(object 
  (object
    (name "croissant")
    (quantity 2))
  (object
    (name "latte")
    (quantity 1)
    (size "tall")))

The S-expression data format used is highly simplified compared to LISP's. There is no support for quote, quasiquote, unquote, or dot pair-builders. The character literal #\ (for space) is not supported either. Use #\space instead. There is also no support for #1234 = ... expressions to construct graphs.


Setup and Installation

  • To build and install this tool, you will need Cargo and a Rust toolchain.

  • Navigate to the root of this repository with a shell, then run:

    cargo install --path .
    
  • To run tests, you will also need bash and Python3


Example Usage

$ cat my-file.sexp | sexpfmt > my-formatted-file.sexp
$ ./build/my-sexp-generator-program arg1 arg2 | sexpfmt >> formatted-logfile.sexp

For examples of sexpfmt's behavior, see the test directory.


TODO

  • allow command line options to specify...
    • whether to print help and exit (e.g. -h or --help)
    • whether to normalize bookend tokens
    • the margin width and indent width.
    • file input, directly map file using OS API to handle very large files.
  • preserve comments when parsing.
  • better error reporting if mis-formatted file is fed as input.
    • e.g. we have almost everything needed to provide line numbers.
  • consider whether to support more features like quote, quasiquote, unquote, pair building, etc.

Dependencies

~1MB
~22K SLoC