created_at2023-06-18 07:46:56.368628
updated_at2024-01-21 11:04:03.543003
descriptionSimple language for config files




SJFL is a simple language for configuration files. SJFL is a (syntactically and semantically) superset of JSON and a (syntactically) subset of Python. That means you can parse JSON files using a SJFL parser, and use Python syntax highlighters for SJFL files.

It's not a general-purpose script language. It's intended for config files. That means it's not turing complete.


  • JSON
    • A valid JSON document is a valid SJFL document.
  • A few extensions on JSON
    • Trailing commas
    • Single quoted strings
    • Comments with #s
    • More ways of representing numbers
      • 0x1234
      • 0b10101
      • 3.1415926535897932384626
        • Most implementations that use floating points cannot represent this value correctly. But this implementation does, thanks to hmath.
      • It also supports arbitrary-precision integers, thanks to hmath.
    • Any valid SJFL value can be a key of a table.
      • For example, {{[] : []} : {[] : []}} is valid in SJFL.
      • There're tradeoffs, though. It cannot check whether a table has multiple same keys.
  • Variables
  • Datetime
    • datetime(2024, 1, 20) is 1st, January, 2024.
    • It takes at most 7 arguments: datetime(2022, 7, 16, 18, 30, 31, 0) where the arguments are year, month, day, hour, minute, second and microsecond. The last 4 arguments are optional. When the optional arguments are missing, the default value 0 is given.


For now, statements are not implemented... at all!

Unlike Python, all the SJFL statements must be followed by a semi-colon.

  • Assignments (TODO)
    • You'll find it useful if you're using SJFL for config files. See the examples below to see what I mean.
    • Rules for a name of a variable is the same as that of most other languages. ([a-zA-Z_] [0-9a-zA-Z]*)
      • There are 7 keywords: true, false, null, True, False, None and import. You cannot use them as a variable name.




Everytime the engine parses a .sjfl file, it generates a binary version in the same directory, with .bsjfl extension. It reads .bsjfl next time if the raw text file has not been modified. It also re-parse the raw-text version if one of its dependency is modified.

Everything is done under the hood, and you don't have to care about it. You just modify .sjfl files, and do not touch .bsjfl files.

(TODO) All the binary conversions are done automatically. All you have to do is call execute_file function.

Commit count: 0

cargo fmt