tbrooke · August 29, 2015 14:04
diff --git a/parser.rb b/parser.rb

 ##  Simple Parser
 ##
 ##  This parser implments an example of a parser similiar to Hoplon or Pollen
 ##  in that it translates an s expression to html
 ##  ie (h1 "The Great Gatsby") produces <h1>The Great Gatsby</h1>
 #
 #
 # Input
 #
 #
 #   Initial S Expression
 #
 # (html
 #   (head
 #     (title "Hello World"))
 #   (body
 #     (h1 "Hello World")
 #     (p "This is your parser")))
 #
 #
 # '(html(head(title "Hello World"))(body (h1 "Hello World")(p "This is your parser")))'
 #
 ##  Converted to nested array of symbols  with class Reader
 ##
 ## parse_string   ==
 ## [:html, [:head, [:title, "Hello World"]], [:body, [:h1, "Hello World"], [:p, "This is your parser"]]]
 ##
 ##
 ###      Finally to HTML
 ###
 ### <html>
 ###      <head>
 ###          <title>Hello World</title>
 ###        </head>
 ###      <body>
 ###        <h1> Hello World </h1>
 ###        <p> This is your parser</p>
 ###      </body>
 ### </html>



 require 'strscan'

 class Reader < StringScanner


  # Check for Missing parens


  def initialize(string)
    unless(string.count('(') == string.count(')'))
      raise Exception, "Missing closing parentheses"
    end
    super(string)
  end


  #  Pull the tokens from the S_Exp into an Array

  def parse
    exp = []
    while true
      case fetch_token
      when '('
        exp << parse
      when ')'
        break
      when :"'"
        case fetch_token
        when '(' then exp << [:quote].concat([parse])
        else exp << [:quote, @token]
        end
      when String, Fixnum, Symbol
        exp << @token
      when nil
        break
      end
    end
    exp
  end

  # Use scan with regex to grab each token

  def fetch_token
    skip(/\s+/)
    return nil if(eos?)

    @token =

      # Match parentheses

    if scan(/[\(\)]/)
      matched

      # Match a string

    elsif scan(/"([^"\\]|\\.)*"/)
      eval(matched)

      # Match an integer

    elsif scan(/[\-\+]?[0-9]+/)
      matched.to_i

      # Match a single quote (for single quoting)

    elsif scan(/'/)
      matched.to_sym

      # Match a symbol

    elsif scan(/[^\(\)\s]+/)
      matched.to_sym

      # If we've gotten here then we have an invalid token

    else
      near = scan %r{.{0,20}}
      raise "Invalid character at position #{pos} near '#{near}'."
    end
  end
 end

 class Parser


  # Parse a string containing an S-Expression into a
  # nested set of Ruby arrays

  def parse_string(string)
    tree = Reader.new(string).parse
    tree = tree[0]     # pull off the outer Array
    return tree
  end


  def to_html(data)
    if (data.is_a?(Array))

      tag = data[0]
      children = data[1..-1]
      return "<#{tag}>" + children.map {|x| to_html(x)}.join(' ') + "</#{tag}>"
    else
      return data
    end
  end


  # Convert a set of nested arrays back into an S-Expression

  def to_sexp(data)
    if( data.is_a?(Array))
      mapped = data.map do |item|
        if( item.is_a?(Array))
          to_sexp(item)
        else
          item.to_s
        end
      end
      "(" + mapped.join(" ") + ")"
    else
      data.to_s
    end
  end

 end

	## Simple Parser
	##
	## This parser implments an example of a parser similiar to Hoplon or Pollen
	## in that it translates an s expression to html
	## ie (h1 "The Great Gatsby") produces <h1>The Great Gatsby</h1>
	#
	#
	# Input
	#
	#
	# Initial S Expression
	#
	# (html
	# (head
	# (title "Hello World"))
	# (body
	# (h1 "Hello World")
	# (p "This is your parser")))
	#
	#
	# '(html(head(title "Hello World"))(body (h1 "Hello World")(p "This is your parser")))'
	#
	## Converted to nested array of symbols with class Reader
	##
	## parse_string ==
	## [:html, [:head, [:title, "Hello World"]], [:body, [:h1, "Hello World"], [:p, "This is your parser"]]]
	##
	##
	### Finally to HTML
	###
	### <html>
	### <head>
	### <title>Hello World</title>
	### </head>
	### <body>
	### <h1> Hello World </h1>
	### <p> This is your parser</p>
	### </body>
	### </html>



	require 'strscan'

	class Reader < StringScanner


	# Check for Missing parens


	def initialize(string)
	unless(string.count('(') == string.count(')'))
	raise Exception, "Missing closing parentheses"
	end
	super(string)
	end


	# Pull the tokens from the S_Exp into an Array

	def parse
	exp = []
	while true
	case fetch_token
	when '('
	exp << parse
	when ')'
	break
	when :"'"
	case fetch_token
	when '(' then exp << [:quote].concat([parse])
	else exp << [:quote, @token]
	end
	when String, Fixnum, Symbol
	exp << @token
	when nil
	break
	end
	end
	exp
	end

	# Use scan with regex to grab each token

	def fetch_token
	skip(/\s+/)
	return nil if(eos?)

	@token =

	# Match parentheses

	if scan(/[\(\)]/)
	matched

	# Match a string

	elsif scan(/"([^"\\]\|\\.)*"/)
	eval(matched)

	# Match an integer

	elsif scan(/[\-\+]?[0-9]+/)
	matched.to_i

	# Match a single quote (for single quoting)

	elsif scan(/'/)
	matched.to_sym

	# Match a symbol

	elsif scan(/[^\(\)\s]+/)
	matched.to_sym

	# If we've gotten here then we have an invalid token

	else
	near = scan %r{.{0,20}}
	raise "Invalid character at position #{pos} near '#{near}'."
	end
	end
	end

	class Parser


	# Parse a string containing an S-Expression into a
	# nested set of Ruby arrays

	def parse_string(string)
	tree = Reader.new(string).parse
	tree = tree[0] # pull off the outer Array
	return tree
	end


	def to_html(data)
	if (data.is_a?(Array))

	tag = data[0]
	children = data[1..-1]
	return "<#{tag}>" + children.map {\|x\| to_html(x)}.join(' ') + "</#{tag}>"
	else
	return data
	end
	end


	# Convert a set of nested arrays back into an S-Expression

	def to_sexp(data)
	if( data.is_a?(Array))
	mapped = data.map do \|item\|
	if( item.is_a?(Array))
	to_sexp(item)
	else
	item.to_s
	end
	end
	"(" + mapped.join(" ") + ")"
	else
	data.to_s
	end
	end

	end