class Racc::Grammar

def init
  return if @closed
  @closed = true
  @start ||= @rules.map {|r| r.target }.detect {|sym| not sym.dummy? }
  raise CompileError, 'no rule in input' if @rules.empty?
  add_start_rule
  @rules.freeze
  fix_ident
  compute_hash
  compute_heads
  determine_terminals
  compute_nullable_0
  @symboltable.fix
  compute_locate
  @symboltable.each_nonterminal {|t| compute_expand t }
  compute_nullable
  compute_useless
end