class Nydp::Symbol
  EMPTY = :""
  attr_accessor :name

  def initialize name
    @name = name.to_sym
    @inspection = name.to_s
    @inspection = "|#{name}|" if untidy(@inspection)
  end

  def untidy str
    (str == "") || (str == nil) || (str =~ /\s/)
  end

  def is? nm
    self.name == nm.to_sym
  end

  def value context=nil
    raise "unbound symbol: #{self.inspect}" if @value == nil
    @value || Nydp.NIL
  end


  def self.mk name, ns
    name = name.to_sym
    return Nydp.NIL if name == :nil
    return Nydp.T   if name == :t
    sym = ns[name]
    unless sym
      sym = new(name)
      ns[name] = sym
    end
    sym
  end

  def self.find name, ns
    ns[name.to_sym]
  end

  def nydp_type ; :symbol     ; end
  def inspect   ; @inspection ; end
  def to_s      ; name.to_s   ; end
  def to_ruby   ; name        ; end

  def == other
    other.is_a?(Nydp::Symbol) && (self.name == other.name)
  end

  def assign value, context=nil
    @value = value
  end
end