davidkellis / arborist Goto Github PK

Are there any plans to support regex? It seems as though Ohm itself doesn't support it, but it would be a nice thing to have.

Hey 👋

thanks for your lib! I'm using it to parse Lisp (Clojure-like) syntax. Here is some feedback (want to share some thoughts with you).

It would be nice to have error object which would contain 1 message (as a string) with line and column. For now I use print_match_failure_error.

For example:

Malformed input fragment on line 1 char 5 ; at position 5 (character index 4):
(1 2
----^
Expected one of the following expressions to match on line 1 char 5 ; at position 5 (character index 4):
number
  1. term(".")
     0 - expression_or_comment
     0 - expression
     0 - list
     3 - expression_or_comment
     3 - expression
     3 - number
comment
  1. term(";")
     0 - expression_or_comment
     0 - expression
     0 - list
     3 - expression_or_comment
     4 - comment
list
  1. term(")")
     0 - expression_or_comment
     0 - expression
     0 - list

In the given example I would expect:

Expected ")" on line 1 at position 5 instead got end of file

Adding ; or . would not fix the sitaution.

I didn't find a good way to skip Lisp-comments, instead I return nil and later check for it:

eval.on("expression_or_comment") do |ctx|
  if ctx.captures["expression"]?
    ctx.capture("expression").visit(eval)
  else
    # return nil to skip
    nil
  end
end

eval.on("list") do |ctx|
  list = Mal::List.new
  if ctx.captures.first_value?
    ctx.captures.first_value.each do |e|
      val = e.visit(eval)
      if val # check if not a comment
        list << val
      end
    end
  end
  Mal::Type.new list
end

I also want to implement Python-like syntax (which would be transformed to s-expressions). I wonder what it would take to implement :python mode?