Convert.Simplifiedval traditional2revised : 
  ('token, 'semantic_value) traditional ->
  ('token * Stdlib.Lexing.position * Stdlib.Lexing.position, 'semantic_value)
    revisedval revised2traditional : 
  ('token * Stdlib.Lexing.position * Stdlib.Lexing.position, 'semantic_value)
    revised ->
  ('token, 'semantic_value) traditional