Ruby & Treetop - No such file or directory @ rb_sysopen

Question

I am trying to learn working with Treetop PEG grammar parser, but I am getting weird error straight from beginning.

I have this file structure

node_extensions.rb parser.rb          tranlan.treetop

And contents of files is following (listings are in order of files listed above)

node_extensions.rb

# node_extensions.rb
module TranLan

end

parser.rb

# parser.rb
require 'treetop'

# Find out what our base path is
base_path = File.expand_path(File.dirname(__FILE__))

# Load our custom syntax node classes so the parser can use them
require File.join(base_path, 'node_extensions.rb')

class Parser
  base_path = File.expand_path(File.dirname(__FILE__))
  Treetop.load(File.join(base_path, 'tranlan_parser.treetop'))
  @@parser = SexpParser.new

  def self.parse(data)
    tree = @@parser.parse(data)
    raise Exception, "Parser error at offset: #{@@parser.index}" if tree.nil?
    tree
  end
end

tranlan.treetop

# tranlan.treetop
grammar TranLan

end

When I run parser.rb, I get this error

/Users/maca/.rvm/gems/ruby-2.1.4/gems/treetop-1.5.3/lib/treetop/compiler/grammar_compiler.rb:37:in `initialize': No such file or directory @ rb_sysopen - /Users/maca/devel/playground/treetop-grammar/tranlan_parser.treetop (Errno::ENOENT)
from /Users/maca/.rvm/gems/ruby-2.1.4/gems/treetop-1.5.3/lib/treetop/compiler/grammar_compiler.rb:37:in `open'
from /Users/maca/.rvm/gems/ruby-2.1.4/gems/treetop-1.5.3/lib/treetop/compiler/grammar_compiler.rb:37:in `load'
from parser.rb:17:in `<class:Parser>'
from parser.rb:10:in `<main>'

What's wrong? Any help?

You've created tranlan.treetop but you're loading tranlan_parser.treetop — Frederick Cheung, Dec 25 '14 at 10:47
@FrederickCheung, please make a regular answer so I can mark it correct answer for that. Thanks a lot. — Martin Macak, Dec 25 '14 at 10:52

score 1 · Accepted Answer · answered Dec 26 '14 at 11:16

You have multiple errors:

You are trying to load tranlan_parser instead of tranlan
You are trying to load a .treetop file but it's called .tt
You are trying to instantiate SexpParser but you created TranLanParser
TranLanParser has no rule, so no top rule, so contains no parser
You don't need to be doing all that fancy filename-munging. Just require the files.
You don't need a Parser class, Treetop generates one for you (re-open it to extend it)

That's a start. Fix those things and you'll be able to start writing a grammar.

Ruby & Treetop - No such file or directory @ rb_sysopen

1 Answers1