  Start     : string = ""    -- start symbol
  xaron     : flag   = false -- create a derivation tree ( lisp like representation )
  early     : flag   = false -- use early reduction
  shiftfun  : string = ""    -- user-defined token conversion: Function@Library ( see [ptm_gen] )
  reducefun : string = ""    -- user-defined nonterminal conversion: Function@Library ( see [ptm_gen] )
