anchor.diff:  %% generators
   -export([list/1,
            tuple/1,
  +         map/0,
            int/0,
            int/1,
            int/2,
  
positive.code:          binary/0,
           non_empty/1,
           resize/2,
           non_neg_integer/0,
           pos_integer/0]).
  
  
negative.code: 
  -record(list,  {elem}).
  -record(tuple, {elem}).
  -record(map,   {size}).
  -record(vector,{size, elem}).
  -record(binary,{size}).
  -record(atom,  {size}).
  