spundun/Gemfile

## README.md

      
    Raw
  

              README.md
            
          
    Trying to follow the tutorial from http://thingsaaronmade.com/blog/a-quick-intro-to-writing-a-parser-using-treetop.html
I get the following error.
spundun$ bundle exec pry
[1] pry(main)> require './parser'
=> true
[2] pry(main)> Parser.parse('(this "is" a test( 1 2.0 3))')
Exception: Parse error at offset: 0
from /Users/spundun/Documents/code_samples/s_expression_parser/parser.rb:35:in `parse'
[3] pry(main)> 

The error goes away if I move the body rule in sexp_parser.treetop from the bottom to the top. (Making it the first rule).
spundun$ bundle exec pry
[1] pry(main)> require './parser'
=> true
[2] pry(main)> Parser.parse('(this "is" a test( 1 2.0 3))')
=> [[:this, "is", :a, :test, [1, 2.0, 3]]]
[3] pry(main)> quit


## Gemfile
gem 'treetop'
gem 'pry'

## Gemfile.lock
GEM
  specs:
    coderay (1.1.0)
    method_source (0.8.2)
    polyglot (0.3.5)
    pry (0.10.1)
      coderay (~> 1.1.0)
      method_source (~> 0.8.1)
      slop (~> 3.4)
    slop (3.6.0)
    treetop (1.5.3)
      polyglot (~> 0.3)

PLATFORMS
  ruby

DEPENDENCIES
  pry
  treetop

## node_extensions.rb
# In file node_extensions.rb
module Sexp
  class IntegerLiteral < Treetop::Runtime::SyntaxNode
    def to_array
      return self.text_value.to_i
    end
  end

  class StringLiteral < Treetop::Runtime::SyntaxNode
    def to_array
      return eval self.text_value
    end
  end

  class FloatLiteral < Treetop::Runtime::SyntaxNode
    def to_array
      return self.text_value.to_f
    end
  end

  class Identifier < Treetop::Runtime::SyntaxNode
    def to_array
      return self.text_value.to_sym
    end
  end

  class Expression < Treetop::Runtime::SyntaxNode
    def to_array
      return self.elements[0].to_array
    end
  end

  class Body < Treetop::Runtime::SyntaxNode
    def to_array
      return self.elements.map {|x| x.to_array}
    end
  end
end

## parser.rb
# In file 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

  # Load the Treetop grammar from the 'sexp_parser' file, and
  # create a new instance of that parser as a class variable
  # so we don't have to re-create it every time we need to
  # parse a string

  # Spundun: Had to add the following line. It seems like the base_path
  # variable initialized above goes out of scope here, I wonder why
  # This error was there in the code I pasted from
  # http://thingsaaronmade.com/blog/a-quick-intro-to-writing-a-parser-using-treetop.html
  # Maybe ruby version issue?
  # Find out what our base path is
  base_path = File.expand_path(File.dirname(__FILE__))

  Treetop.load(File.join(base_path, 'sexp_parser.treetop'))
  @@parser = SexpParser.new

  def self.parse(data)
    # Pass the data over to the parser instance
    tree = @@parser.parse(data)

    # If the AST is nil then there was an error during parsing
    # we need to report a simple error message to help the user
    if(tree.nil?)
      raise Exception, "Parse error at offset: #{@@parser.index}"
    end

    self.clean_tree(tree)

    return tree.to_array
  end

  private
    def self.clean_tree(root_node)
      return if(root_node.elements.nil?)
      root_node.elements.delete_if{|node| node.class.name == "Treetop::Runtime::SyntaxNode" }
      root_node.elements.each {|node| self.clean_tree(node) }
    end
end

## sexp_parser.treetop
# In file sexp_extensions.rb
grammar Sexp
  rule integer
    ('+' / '-')? [0-9]+ <IntegerLiteral>
  end

  rule float
    ('+' / '-')? [0-9]+ (('.' [0-9]+) / ('e' [0-9]+)) <FloatLiteral>
  end

  rule string
    '"' ([^"\\] / "\\" . )* '"' <StringLiteral>
  end

  rule identifier
    [a-zA-Z\=\*] [a-zA-Z0-9_\=\*]* <Identifier>
  end

  rule space
    [\s]+
  end

  rule expression
    space? '(' body ')' space? <Expression>
  end

  rule body
    (expression / identifier / float / integer / string / space )* <Body>
  end
end
	GEM
	specs:
	coderay (1.1.0)
	method_source (0.8.2)
	polyglot (0.3.5)
	pry (0.10.1)
	coderay (~> 1.1.0)
	method_source (~> 0.8.1)
	slop (~> 3.4)
	slop (3.6.0)
	treetop (1.5.3)
	polyglot (~> 0.3)

	PLATFORMS
	ruby

	DEPENDENCIES
	pry
	treetop
	# In file node_extensions.rb
	module Sexp
	class IntegerLiteral < Treetop::Runtime::SyntaxNode
	def to_array
	return self.text_value.to_i
	end
	end

	class StringLiteral < Treetop::Runtime::SyntaxNode
	def to_array
	return eval self.text_value
	end
	end

	class FloatLiteral < Treetop::Runtime::SyntaxNode
	def to_array
	return self.text_value.to_f
	end
	end

	class Identifier < Treetop::Runtime::SyntaxNode
	def to_array
	return self.text_value.to_sym
	end
	end

	class Expression < Treetop::Runtime::SyntaxNode
	def to_array
	return self.elements[0].to_array
	end
	end

	class Body < Treetop::Runtime::SyntaxNode
	def to_array
	return self.elements.map {\|x\| x.to_array}
	end
	end
	end
	# In file 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

	# Load the Treetop grammar from the 'sexp_parser' file, and
	# create a new instance of that parser as a class variable
	# so we don't have to re-create it every time we need to
	# parse a string

	# Spundun: Had to add the following line. It seems like the base_path
	# variable initialized above goes out of scope here, I wonder why
	# This error was there in the code I pasted from
	# http://thingsaaronmade.com/blog/a-quick-intro-to-writing-a-parser-using-treetop.html
	# Maybe ruby version issue?
	# Find out what our base path is
	base_path = File.expand_path(File.dirname(__FILE__))

	Treetop.load(File.join(base_path, 'sexp_parser.treetop'))
	@@parser = SexpParser.new

	def self.parse(data)
	# Pass the data over to the parser instance
	tree = @@parser.parse(data)

	# If the AST is nil then there was an error during parsing
	# we need to report a simple error message to help the user
	if(tree.nil?)
	raise Exception, "Parse error at offset: #{@@parser.index}"
	end

	self.clean_tree(tree)

	return tree.to_array
	end

	private
	def self.clean_tree(root_node)
	return if(root_node.elements.nil?)
	root_node.elements.delete_if{\|node\| node.class.name == "Treetop::Runtime::SyntaxNode" }
	root_node.elements.each {\|node\| self.clean_tree(node) }
	end
	end
	# In file sexp_extensions.rb
	grammar Sexp
	rule integer
	('+' / '-')? [0-9]+ <IntegerLiteral>
	end

	rule float
	('+' / '-')? [0-9]+ (('.' [0-9]+) / ('e' [0-9]+)) <FloatLiteral>
	end

	rule string
	'"' ([^"\\] / "\\" . )* '"' <StringLiteral>
	end

	rule identifier
	[a-zA-Z\=\] [a-zA-Z0-9_\=\]* <Identifier>
	end

	rule space
	[\s]+
	end

	rule expression
	space? '(' body ')' space? <Expression>
	end

	rule body
	(expression / identifier / float / integer / string / space )* <Body>
	end
	end