rewriting parser confuses variables with symbols

The "1" is sometimes seen as a function symbol, and othertimes, as a variable.

  test/Format.hs:51: 
  2) 133 : Completion-Direct toDoc . reader . toDoc == toDoc  for   default instance
       expected: Just (Right "Problem\n    { equations = [ ( a (b (a (1)))\n                    , 1\n                    )\n                  ]\n    , order_restriction = Polynomial \n    }")
        but got: Just (Right "Problem\n    { equations = [ ( a (b (a (1 )))\n                    , 1 \n                    )\n                  ]\n    , order_restriction = Polynomial \n    }")