Test Case 1: Four highly ambiguous abstract grammars

1. s    = term `x` *> s *> s <+> empty
2. sm   = memoize SM $ term `x` *> sm *> sm <+> empty
3. sml  = memoize SML $ sml *> sml *> term `x` <+> empty
4. smml = memoize SMML $ smml *> (memoize SMML` $ smml *> term `x`) <+> empty

Input length No. of parses    s     sm     sml     smml
-------------------------------------------------------
  6                 132      1.22    -      -       -
  12            208,012       *      -      -      0.02
  24          1.289e+12       *     0.08   0.13    0.06
  48          1.313e+26       *     0.83   0.97    0.80