hindent 2.1.0

Provides functions to translate and/or execute Hindent code.

Hindent is a syntax wrapper around lisps. It simply allows you to use hanging indents as a way to nest parenthesis. For example:

; Hindent

+
  2
  2

; lisp

(+ 2 2)

; example.hin has more examples

Example

Example code: example.hin

The easiest way to think about it is to repeat the following:

• Focus on the the deepest nesting level. This is the current chunk.
• Follow the chunk upward and leftward to where the nearest dedent is, which we call the lead.
• Collapse the chunk's newlines and indentation, wrap it in parenthesis, and leave it where the lead was.

Let's do an example step-by-step

+
  -
    4
    1
  2

Focus on the part with deepest nesting. In this case, it is the 4 and 1. Then track upwards to find the lead, which is -. Then collapse, wrap in parenthesis, and leave it where the lead was.

+
  (- 4 1)
  2

Do it again. Focus on the deepest nesting. In this case, it is (- 4 1) and 2. Follow upward and to the left to find the lead, which is +. Collapse, wrap in parenthesis, and leave where the lead was

(+ (- 4 1) 2)

Or another way to think about it is to do the same thing, but simply insert the parenthesis instead of collapsing. For example

+
  -
    4
    1
  2

; goes to

+
  (-
    4
    1)
  2

; which goes to

(+
  (-
    4
    1)
  2)

It's the same either way because the lisps we're translating to don't mind whitespace.

How it works

Hindent simply parses the Hindent code and inserts parenthesis according to the specification. And as a side feature, it also will let you run that code in a lisp if you want to.

Installation

1. pip install hindent
2. Install clojure and make sure it's on your path by running clojure -Sdescribe.
   • This also works with other lisps or schemes. If you want to do that, the notes in the module dosctrings explain how to use a different lisp
3. The syntax highlighter for vs code is Hindent Lang. You can find it in the normal extensions menu / marketplace.

Usage

I think a nice way to interactively run programs is with jupyter. So, I recommend opening up a jupyter notebook. Then, simply start to import Hindent with import Hindent as h, and the docstrings/code-hover will guide you from there.

Parsing Spec

• the translater supports literate programming. It does so by putting block comments on equal footing with code. To toggle back and forth between code and block comment, put a lone period on a line.
  • For reasons of textmate grammars and syntax highlighting, we had to make the file start as code, rather than starting as block comment. We would have preferred it the other way, but we think it's okay. We're thankful for how awesome vs code and textmate are.
• the parser/translater will put a new line after the source code to ensure the final dedent is correct
• any amount of whitespace that contributes to a blank line (other than the last line) should be replaced with a single new line character. For example, \n\n\n should be replaced with \n, and \n \n should also be replaced with \n
• lines that start with ; are comments and will be ignored
• calculate the number of spaces each line starts with.
• Then divide by 2 to determine the indentation level
• then, for each line find the difference in indentation level between that line and the following line
  • if the indentation level goes up one, then add an opening parenthesis before the line
  • if the indentation level goes down, then add a closing parenthesis after the line according to the number of dedents.
  • if the indentation level remains the same, then we have to check one more thing:
    • if the current indentation level (and also the indentation level of the following line) is at 0, and it isn't already wrapped in parenthesis, then wrap the current line in parenthesis
    • if the current indentation level (and also the indentation level of the following line) is nonzero, then do nothing
• to allow the user to override the indenting and indent the code without hindent paying attention to the indent, you can put a . before a line of code at the indent level you want that code to be treated as. There is an example in example.hin

Miscellaneous Thoughts

This framework works for any language. We just mostly discuss lisps because it has the biggest impact and is cleanest on lisps.

One heads up is that if you try to use it on languages that are whitespace-sensitive (haskell, python, etc), it will probably have trouble because it could theoretically change indentation while inserting parenthesis or removing the hindent markup.

In general, I think translating into whitespace-sensitive languages is probably harder than translating into whitespace-insensitive languages. But translating from whitespace-sensitive languages (like Hindent) is totally okay.

ToDo

• change the verbage from translate to something else. I can't think of what. It's hard to say. really all it does is remove comments and whitespace then add parenthesis.
• maybe get it out of running as a subprocess so it returns things more easily
• make a sphinx site
  • convert readme to rst (change in pyproject.toml as well)
• push to conda (in addition to pypi)

Notes For Grant

• flit build --format wheel
• twine upload dist/*