ruby2ruby.rb

#!/usr/bin/env ruby -w

require 'rubygems'
require 'sexp_processor'

# :stopdoc:
# REFACTOR: stolen from ruby_parser
class Regexp
  unless defined? ENC_NONE then
    ENC_NONE = /x/n.options
    ENC_EUC  = /x/e.options
    ENC_SJIS = /x/s.options
    ENC_UTF8 = /x/u.options

    CODES = {
      EXTENDED   => 'x',
      IGNORECASE => 'i',
      MULTILINE  => 'm',
      ENC_NONE   => 'n',
      ENC_EUC    => 'e',
      ENC_SJIS   => 's',
      ENC_UTF8   => 'u',
    }
  end
end
# :startdoc:

##
# Generate ruby code from a sexp.

class Ruby2Ruby < SexpProcessor
  VERSION = "2.0.4" # :nodoc:

  # cutoff for one-liners
  LINE_LENGTH = 78

  # binary operation messages
  BINARY = [:<=>, :==, :<, :>, :<=, :>=, :-, :+, :*, :/, :%, :<<, :>>, :**]

  ##
  # Nodes that represent assignment and probably need () around them.
  #
  # TODO: this should be replaced with full precedence support :/

  ASSIGN_NODES = [
                  :dasgn,
                  :flip2,
                  :flip3,
                  :lasgn,
                  :masgn,
                  :attrasgn,
                  :op_asgn1,
                  :op_asgn2,
                  :op_asgn_and,
                  :op_asgn_or,
                  :return,
                  :if, # HACK
                 ]

  def initialize # :nodoc:
    super
    @indent = "  "
    self.auto_shift_type = true
    self.strict = true
    self.expected = String

    @calls = []

    # self.debug[:defn] = /zsuper/
  end

  ############################################################
  # Processors

  def process_alias(exp) # :nodoc:
    parenthesize "alias #{process(exp.shift)} #{process(exp.shift)}"
  end

  def process_and(exp) # :nodoc:
    parenthesize "#{process exp.shift} and #{process exp.shift}"
  end

  def process_arglist(exp) # custom made node # :nodoc:
    code = []
    until exp.empty? do
      code << process(exp.shift)
    end
    code.join ', '
  end

  def process_args(exp) # :nodoc:
    args = []

    until exp.empty? do
      arg = exp.shift
      case arg
      when Symbol then
        args << arg
      when Sexp then
        case arg.first
        when :lasgn then
          args << process(arg)
        else
          raise "unknown arg type #{arg.first.inspect}"
        end
      else
        raise "unknown arg type #{arg.inspect}"
      end
    end

    "(#{args.join ', '})"
  end

  def process_array(exp) # :nodoc:
    "[#{process_arglist(exp)}]"
  end

  def process_attrasgn(exp) # :nodoc:
    receiver = process exp.shift
    name = exp.shift
    args = exp.empty? ? nil : exp.shift

    case name
    when :[]= then
      rhs = exp.empty? ? nil : exp.shift
      "#{receiver}[#{process args}] = #{process rhs}"
    else
      name = name.to_s.sub(/=$/, '')
      if args && args != s(:arglist) then
        "#{receiver}.#{name} = #{process(args)}"
      end
    end
  end

  def process_back_ref(exp) # :nodoc:
    "$#{exp.shift}"
  end

  # TODO: figure out how to do rescue and ensure ENTIRELY w/o begin
  def process_begin(exp) # :nodoc:
    code = []
    code << "begin"
    until exp.empty?
      src = process(exp.shift)
      src = indent(src) unless src =~ /(^|\n)(rescue|ensure)/ # ensure no level 0 rescues
      code << src
    end
    code << "end"
    return code.join("\n")
  end

  def process_block(exp) # :nodoc:
    result = []

    exp << nil if exp.empty?
    until exp.empty? do
      code = exp.shift
      if code.nil? or code.first == :nil then
        result << "# do nothing\n"
      else
        result << process(code)
      end
    end

    result = parenthesize result.join "\n"
    result += "\n" unless result.start_with? "("

    return result
  end

  def process_block_pass exp # :nodoc:
    raise "huh?: #{exp.inspect}" if exp.size > 1

    "&#{process exp.shift}"
  end

  def process_break(exp) # :nodoc:
    val = exp.empty? ? nil : process(exp.shift)
    # HACK "break" + (val ? " #{val}" : "")
    if val then
      "break #{val}"
    else
      "break"
    end
  end

  def process_call(exp) # :nodoc:
    receiver_node_type = exp.first.nil? ? nil : exp.first.first
    receiver = process exp.shift
    receiver = "(#{receiver})" if ASSIGN_NODES.include? receiver_node_type

    name = exp.shift
    args = []

    # this allows us to do both old and new sexp forms:
    exp.push(*exp.pop[1..-1]) if exp.size == 1 && exp.first.first == :arglist

    @calls.push name

    in_context :arglist do
      until exp.empty? do
        arg_type = exp.first.sexp_type
        is_empty_hash = (exp.first == s(:hash))
        arg = process exp.shift

        next if arg.empty?

        strip_hash = (arg_type == :hash and
                      not BINARY.include? name and
                      not is_empty_hash and
                      (exp.empty? or exp.first.sexp_type == :splat))
        wrap_arg = Ruby2Ruby::ASSIGN_NODES.include? arg_type

        arg = arg[2..-3] if strip_hash
        arg = "(#{arg})" if wrap_arg

        args << arg
      end
    end

    case name
    when *BINARY then
      "(#{receiver} #{name} #{args.join(', ')})"
    when :[] then
      receiver ||= "self"
      "#{receiver}[#{args.join(', ')}]"
    when :[]= then
      receiver ||= "self"
      rhs = args.pop
      "#{receiver}[#{args.join(', ')}] = #{rhs}"
    when :"!" then
      "(not #{receiver})"
    when :"-@" then
      "-#{receiver}"
    when :"+@" then
      "+#{receiver}"
    else
      args     = nil                    if args.empty?
      args     = "(#{args.join(', ')})" if args
      receiver = "#{receiver}."         if receiver

      "#{receiver}#{name}#{args}"
    end
  ensure
    @calls.pop
  end

  def process_case(exp) # :nodoc:
    result = []
    expr = process exp.shift
    if expr then
      result << "case #{expr}"
    else
      result << "case"
    end
    until exp.empty?
      pt = exp.shift
      if pt and pt.first == :when
        result << "#{process(pt)}"
      else
        code = indent(process(pt))
        code = indent("# do nothing") if code =~ /^\s*$/
        result << "else\n#{code}"
      end
    end
    result << "end"
    result.join("\n")
  end

  def process_cdecl(exp) # :nodoc:
    lhs = exp.shift
    lhs = process lhs if Sexp === lhs
    unless exp.empty? then
      rhs = process(exp.shift)
      "#{lhs} = #{rhs}"
    else
      lhs.to_s
    end
  end

  def process_class(exp) # :nodoc:
    "#{exp.comments}class #{util_module_or_class(exp, true)}"
  end

  def process_colon2(exp) # :nodoc:
    "#{process(exp.shift)}::#{exp.shift}"
  end

  def process_colon3(exp) # :nodoc:
    "::#{exp.shift}"
  end

  def process_const(exp) # :nodoc:
    exp.shift.to_s
  end

  def process_cvar(exp) # :nodoc:
    "#{exp.shift}"
  end

  def process_cvasgn(exp) # :nodoc:
    "#{exp.shift} = #{process(exp.shift)}"
  end

  def process_cvdecl(exp) # :nodoc:
    "#{exp.shift} = #{process(exp.shift)}"
  end

  def process_defined(exp) # :nodoc:
    "defined? #{process(exp.shift)}"
  end

  def process_defn(exp) # :nodoc:
    type1 = exp[1].first
    type2 = exp[2].first rescue nil

    if type1 == :args and [:ivar, :iasgn, :attrset].include? type2 then
      name = exp.first # don't shift in case we pass through
      case type2
      when :ivar then
        ivar_name = exp.ivar.last

        meth_name = ivar_name.to_s[1..-1].to_sym
        expected = s(meth_name, s(:args), s(:ivar, ivar_name))

        if exp == expected then
          exp.clear
          return "attr_reader #{name.inspect}"
        end
      when :attrset then
        # TODO: deprecate? this is a PT relic
        exp.clear
        return "attr_writer :#{name.to_s[0..-2]}"
      when :iasgn then
        ivar_name = exp.iasgn[1]
        meth_name = "#{ivar_name.to_s[1..-1]}=".to_sym
        arg_name = exp.args.last
        expected = s(meth_name, s(:args, arg_name),
                     s(:iasgn, ivar_name, s(:lvar, arg_name)))

        if exp == expected then
          exp.clear
          return "attr_writer :#{name.to_s[0..-2]}"
        end
      else
        raise "Unknown defn type: #{exp.inspect}"
      end
    end

    comm = exp.comments
    name = exp.shift
    args = process exp.shift
    args = "" if args == "()"

    exp.shift if exp == s(s(:nil)) # empty it out of a default nil expression

    body = []
    until exp.empty? do
      body << indent(process(exp.shift))
    end

    body << indent("# do nothing") if body.empty?

    body = body.join("\n")

    return "#{comm}def #{name}#{args}\n#{body}\nend".gsub(/\n\s*\n+/, "\n")
  end

  def process_defs(exp) # :nodoc:
    lhs  = exp.shift
    var = [:self, :cvar, :dvar, :ivar, :gvar, :lvar].include? lhs.first
    name = exp.shift

    lhs = process(lhs)
    lhs = "(#{lhs})" unless var

    exp.unshift "#{lhs}.#{name}"
    process_defn(exp)
  end

  def process_dot2(exp) # :nodoc:
    "(#{process exp.shift}..#{process exp.shift})"
  end

  def process_dot3(exp) # :nodoc:
    "(#{process exp.shift}...#{process exp.shift})"
  end

  def process_dregx(exp) # :nodoc:
    options = re_opt exp.pop if Fixnum === exp.last
    "/" << util_dthing(:dregx, exp) << "/#{options}"
  end

  def process_dregx_once(exp) # :nodoc:
    process_dregx(exp) + "o"
  end

  def process_dstr(exp) # :nodoc:
    "\"#{util_dthing(:dstr, exp)}\""
  end

  def process_dsym(exp) # :nodoc:
    ":\"#{util_dthing(:dsym, exp)}\""
  end

  def process_dxstr(exp) # :nodoc:
    "`#{util_dthing(:dxstr, exp)}`"
  end

  def process_ensure(exp) # :nodoc:
    body = process exp.shift
    ens  = exp.shift
    ens  = nil if ens == s(:nil)
    ens  = process(ens) || "# do nothing"
    ens = "begin\n#{ens}\nend\n" if ens =~ /(^|\n)rescue/

    body.sub!(/\n\s*end\z/, '')
    body = indent(body) unless body =~ /(^|\n)rescue/

    return "#{body}\nensure\n#{indent ens}"
  end

  def process_evstr(exp) # :nodoc:
    exp.empty? ? '' : process(exp.shift)
  end

  def process_false(exp) # :nodoc:
    "false"
  end

  def process_flip2(exp) # :nodoc:
    "#{process(exp.shift)}..#{process(exp.shift)}"
  end

  def process_flip3(exp) # :nodoc:
    "#{process(exp.shift)}...#{process(exp.shift)}"
  end

  def process_for(exp) # :nodoc:
    recv = process exp.shift
    iter = process exp.shift
    body = exp.empty? ? nil : process(exp.shift)

    result = ["for #{iter} in #{recv} do"]
    result << indent(body ? body : "# do nothing")
    result << "end"

    result.join("\n")
  end

  def process_gasgn(exp) # :nodoc:
    process_iasgn(exp)
  end

  def process_gvar(exp) # :nodoc:
    return exp.shift.to_s
  end

  def process_hash(exp) # :nodoc:
    result = []

    until exp.empty?
      lhs = process(exp.shift)
      rhs = exp.shift
      t = rhs.first
      rhs = process rhs
      rhs = "(#{rhs})" unless [:lit, :str].include? t # TODO: verify better!

      result << "#{lhs} => #{rhs}"
    end

    return result.empty? ? "{}" : "{ #{result.join(', ')} }"
  end

  def process_iasgn(exp) # :nodoc:
    lhs = exp.shift
    if exp.empty? then # part of an masgn
      lhs.to_s
    else
      "#{lhs} = #{process exp.shift}"
    end
  end

  def process_if(exp) # :nodoc:
    expand = Ruby2Ruby::ASSIGN_NODES.include? exp.first.first
    c = process exp.shift
    t = process exp.shift
    f = process exp.shift

    c = "(#{c.chomp})" if c =~ /\n/

    if t then
      unless expand then
        if f then
          r = "#{c} ? (#{t}) : (#{f})"
          r = nil if r =~ /return/ # HACK - need contextual awareness or something
        else
          r = "#{t} if #{c}"
        end
        return r if r and (@indent+r).size < LINE_LENGTH and r !~ /\n/
      end

      r = "if #{c} then\n#{indent(t)}\n"
      r << "else\n#{indent(f)}\n" if f
      r << "end"

      r
    elsif f
      unless expand then
        r = "#{f} unless #{c}"
        return r if (@indent+r).size < LINE_LENGTH and r !~ /\n/
      end
      "unless #{c} then\n#{indent(f)}\nend"
    else
      # empty if statement, just do it in case of side effects from condition
      "if #{c} then\n#{indent '# do nothing'}\nend"
    end
  end

  def process_iter(exp) # :nodoc:
    iter = process exp.shift
    args = exp.shift
    body = exp.empty? ? nil : process(exp.shift)

    args = case args
           when 0 then
             " ||"
           else
             a = process(args)[1..-2]
             a = " |#{a}|" unless a.empty?
             a
           end

    b, e = if iter == "END" then
             [ "{", "}" ]
           else
             [ "do", "end" ]
           end

    iter.sub!(/\(\)$/, '')

    # REFACTOR: ugh
    result = []
    result << "#{iter} {"
    result << args
    if body then
      result << " #{body.strip} "
    else
      result << ' '
    end
    result << "}"
    result = result.join
    return result if result !~ /\n/ and result.size < LINE_LENGTH

    result = []
    result << "#{iter} #{b}"
    result << args
    result << "\n"
    if body then
      result << indent(body.strip)
      result << "\n"
    end
    result << e
    result.join
  end

  def process_ivar(exp) # :nodoc:
    exp.shift.to_s
  end

  def process_lasgn(exp) # :nodoc:
    s = "#{exp.shift}"
    s += " = #{process exp.shift}" unless exp.empty?
    s
  end

  def process_lit(exp) # :nodoc:
    obj = exp.shift
    case obj
    when Range then
      "(#{obj.inspect})"
    else
      obj.inspect
    end
  end

  def process_lvar(exp) # :nodoc:
    exp.shift.to_s
  end

  def process_masgn(exp) # :nodoc:
    lhs = exp.shift
    rhs = exp.empty? ? nil : exp.shift

    case lhs.first
    when :array then
      lhs.shift
      lhs = lhs.map do |l|
        case l.first
        when :masgn then
          "(#{process(l)})"
        else
          process(l)
        end
      end
    when :lasgn then
      lhs = [ splat(lhs.last) ]
    when :splat then
      lhs = [ :"*" ]
    else
      raise "no clue: #{lhs.inspect}"
    end

    if context[1] == :iter and rhs then
      lhs << splat(rhs[1])
      rhs = nil
    end

    unless rhs.nil? then
      t = rhs.first
      rhs = process rhs
      rhs = rhs[1..-2] if t == :array # FIX: bad? I dunno
      return "#{lhs.join(", ")} = #{rhs}"
    else
      return lhs.join(", ")
    end
  end

  def process_match(exp) # :nodoc:
    "#{process(exp.shift)}"
  end

  def process_match2(exp) # :nodoc:
    lhs = process(exp.shift)
    rhs = process(exp.shift)
    "#{lhs} =~ #{rhs}"
  end

  def process_match3(exp) # :nodoc:
    rhs = process(exp.shift)
    left_type = exp.first.sexp_type
    lhs = process(exp.shift)

    if ASSIGN_NODES.include? left_type then
      "(#{lhs}) =~ #{rhs}"
    else
      "#{lhs} =~ #{rhs}"
    end
  end

  def process_module(exp) # :nodoc:
    "#{exp.comments}module #{util_module_or_class(exp)}"
  end

  def process_next(exp) # :nodoc:
    val = exp.empty? ? nil : process(exp.shift)
    if val then
      "next #{val}"
    else
      "next"
    end
  end

  def process_nil(exp) # :nodoc:
    "nil"
  end

  def process_not(exp) # :nodoc:
    "(not #{process exp.shift})"
  end

  def process_nth_ref(exp) # :nodoc:
    "$#{exp.shift}"
  end

  def process_op_asgn1(exp) # :nodoc:
    # [[:lvar, :b], [:arglist, [:lit, 1]], :"||", [:lit, 10]]
    lhs = process(exp.shift)
    index = process(exp.shift)
    msg = exp.shift
    rhs = process(exp.shift)

    "#{lhs}[#{index}] #{msg}= #{rhs}"
  end

  def process_op_asgn2(exp) # :nodoc:
    # [[:lvar, :c], :var=, :"||", [:lit, 20]]
    lhs = process(exp.shift)
    index = exp.shift.to_s[0..-2]
    msg = exp.shift

    rhs = process(exp.shift)

    "#{lhs}.#{index} #{msg}= #{rhs}"
  end

  def process_op_asgn_and(exp) # :nodoc:
    # a &&= 1
    # [[:lvar, :a], [:lasgn, :a, [:lit, 1]]]
    exp.shift
    process(exp.shift).sub(/\=/, '&&=')
  end

  def process_op_asgn_or(exp) # :nodoc:
    # a ||= 1
    # [[:lvar, :a], [:lasgn, :a, [:lit, 1]]]
    exp.shift
    process(exp.shift).sub(/\=/, '||=')
  end

  def process_or(exp) # :nodoc:
    "(#{process exp.shift} or #{process exp.shift})"
  end

  def process_postexe(exp) # :nodoc:
    "END"
  end

  def process_redo(exp) # :nodoc:
    "redo"
  end

  def process_resbody exp # :nodoc:
    args = exp.shift
    body = finish(exp)
    body << "# do nothing" if body.empty?

    name =   args.lasgn true
    name ||= args.iasgn true
    args = process(args)[1..-2]
    args = " #{args}" unless args.empty?
    args += " => #{name[1]}" if name

    "rescue#{args}\n#{indent body.join("\n")}"
  end

  def process_rescue exp # :nodoc:
    body = process(exp.shift) unless exp.first.first == :resbody
    els  = process(exp.pop)   unless exp.last.first  == :resbody

    body ||= "# do nothing"
    simple = exp.size == 1 && !exp.resbody.block


    resbodies = []
    until exp.empty? do
      resbody = exp.shift
      simple &&= resbody[1] == s(:array)
      simple &&= resbody[2] != nil && resbody[2].node_type != :block
      resbodies << process(resbody)
    end

    if els then
      "#{indent body}\n#{resbodies.join("\n")}\nelse\n#{indent els}"
    elsif simple then
      resbody = resbodies.first.sub(/\n\s*/, ' ')
      "#{body} #{resbody}"
    else
      "#{indent body}\n#{resbodies.join("\n")}"
    end
  end

  def process_retry(exp) # :nodoc:
    "retry"
  end

  def process_return(exp) # :nodoc:
    # HACK return "return" + (exp.empty? ? "" : " #{process exp.shift}")

    if exp.empty? then
      return "return"
    else
      return "return #{process exp.shift}"
    end
  end

  def process_sclass(exp) # :nodoc:
    "class << #{process(exp.shift)}\n#{indent(process(exp.shift))}\nend"
  end

  def process_self(exp) # :nodoc:
    "self"
  end

  def process_splat(exp) # :nodoc:
    if exp.empty? then
      "*"
    else
      "*#{process(exp.shift)}"
    end
  end

  def process_str(exp) # :nodoc:
    return exp.shift.dump
  end

  def process_super(exp) # :nodoc:
    args = finish exp

    "super(#{args.join(', ')})"
  end

  def process_svalue(exp) # :nodoc:
    code = []
    until exp.empty? do
      code << process(exp.shift)
    end
    code.join(", ")
  end

  def process_to_ary(exp) # :nodoc:
    process(exp.shift)
  end

  def process_true(exp) # :nodoc:
    "true"
  end

  def process_undef(exp) # :nodoc:
    "undef #{process(exp.shift)}"
  end

  def process_until(exp) # :nodoc:
    cond_loop(exp, 'until')
  end

  def process_valias(exp) # :nodoc:
    "alias #{exp.shift} #{exp.shift}"
  end

  def process_when(exp) # :nodoc:
    src = []

    if self.context[1] == :array then # ugh. matz! why not an argscat?!?
      val = process(exp.shift)
      exp.shift # empty body
      return "*#{val}"
    end

    until exp.empty?
      cond = process(exp.shift).to_s[1..-2]
      code = indent(finish(exp).join("\n"))
      code = indent "# do nothing" if code =~ /\A\s*\Z/
      src << "when #{cond} then\n#{code.chomp}"
    end

    src.join("\n")
  end

  def process_while(exp) # :nodoc:
    cond_loop(exp, 'while')
  end

  def process_xstr(exp) # :nodoc:
    "`#{process_str(exp)[1..-2]}`"
  end

  def process_yield(exp) # :nodoc:
    args = []
    until exp.empty? do
      args << process(exp.shift)
    end

    unless args.empty? then
      "yield(#{args.join(', ')})"
    else
      "yield"
    end
  end

  def process_zsuper(exp) # :nodoc:
    "super"
  end

  ############################################################
  # Rewriters:

  def rewrite_attrasgn exp # :nodoc:
    if context.first(2) == [:array, :masgn] then
      exp[0] = :call
      exp[2] = exp[2].to_s.sub(/=$/, '').to_sym
    end

    exp
  end

  def rewrite_ensure exp # :nodoc:
    exp = s(:begin, exp) unless context.first == :begin
    exp
  end

  def rewrite_resbody exp # :nodoc:
    raise "no exception list in #{exp.inspect}" unless exp.size > 2 && exp[1]
    raise exp[1].inspect if exp[1][0] != :array
    # for now, do nothing, just check and freak if we see an errant structure
    exp
  end

  def rewrite_rescue exp # :nodoc:
    complex = false
    complex ||= exp.size > 3
    complex ||= exp.resbody.block
    complex ||= exp.find_nodes(:resbody).any? { |n| n[1] != s(:array) }
    complex ||= exp.find_nodes(:resbody).any? { |n| n.last.nil? }
    complex ||= exp.find_nodes(:resbody).any? { |n| n[2] and n[2].node_type == :block }

    handled = context.first == :ensure

    exp = s(:begin, exp) if complex unless handled

    exp
  end

  def rewrite_svalue(exp) # :nodoc:
    case exp.last.first
    when :array
      s(:svalue, *exp[1][1..-1])
    when :splat
      exp
    else
      raise "huh: #{exp.inspect}"
    end
  end

  ############################################################
  # Utility Methods:

  ##
  # Generate a post-or-pre conditional loop.

  def cond_loop(exp, name)
    cond = process(exp.shift)
    body = process(exp.shift)
    head_controlled = exp.shift

    body = indent(body).chomp if body

    code = []
    if head_controlled then
      code << "#{name} #{cond} do"
      code << body if body
      code << "end"
    else
      code << "begin"
      code << body if body
      code << "end #{name} #{cond}"
    end
    code.join("\n")
  end

  ##
  # Utility method to escape something interpolated.

  def dthing_escape type, lit
    lit = lit.gsub(/\n/, '\n')
    case type
    when :dregx then
      lit.gsub(/(\A|[^\\])\//, '\1\/')
    when :dstr, :dsym then
      lit.gsub(/"/, '\"')
    when :dxstr then
      lit.gsub(/`/, '\`')
    else
      raise "unsupported type #{type.inspect}"
    end
  end

  ##
  # Process all the remaining stuff in +exp+ and return the results
  # sans-nils.

  def finish exp # REFACTOR: work this out of the rest of the processors
    body = []
    until exp.empty? do
      body << process(exp.shift)
    end
    body.compact
  end

  ##
  # Indent all lines of +s+ to the current indent level.

  def indent(s)
    s.to_s.split(/\n/).map{|line| @indent + line}.join("\n")
  end

  ##
  # Wrap appropriate expressions in matching parens.

  def parenthesize exp
    case self.context[1]
    when nil, :defn, :defs, :class, :sclass, :if, :iter, :resbody, :when, :while then
      exp
    else
      "(#{exp})"
    end
  end

  ##
  # Return the appropriate regexp flags for a given numeric code.

  def re_opt options
    bits = (0..8).map { |n| options[n] * 2**n }
    bits.delete 0
    bits.map { |n| Regexp::CODES[n] }.join
  end

  ##
  # Return a splatted symbol for +sym+.

  def splat(sym)
    :"*#{sym}"
  end

  ##
  # Utility method to generate something interpolated.

  def util_dthing(type, exp)
    s = []

    # first item in sexp is a string literal
    s << dthing_escape(type, exp.shift)

    until exp.empty?
      pt = exp.shift
      case pt
      when Sexp then
        case pt.first
        when :str then
          s << dthing_escape(type, pt.last)
        when :evstr then
          s << '#{' << process(pt) << '}' # do not use interpolation here
        else
          raise "unknown type: #{pt.inspect}"
        end
      else
        raise "unhandled value in d-thing: #{pt.inspect}"
      end
    end

    s.join
  end

  ##
  # Utility method to generate ether a module or class.

  def util_module_or_class(exp, is_class=false)
    result = []

    name = exp.shift
    name = process name if Sexp === name

    result << name

    if is_class then
      superk = process(exp.shift)
      result << " < #{superk}" if superk
    end

    result << "\n"

    body = []
    begin
      code = process(exp.shift) unless exp.empty?
      body << code.chomp unless code.nil? or code.chomp.empty?
    end until exp.empty?

    unless body.empty? then
      body = indent(body.join("\n\n")) + "\n"
    else
      body = ""
    end
    result << body
    result << "end"

    result.join
  end
end