5 

     5 

     6 (* 

     6 (* 

     7   plain nominal_datatype definition without an 

     7   plain nominal_datatype definition without an 

     8   atom_decl - example by John Matthews

     8   atom_decl - example by John Matthews

     9 *)

     9 *)

    11 

    10 

    12 nominal_datatype 'a Maybe = 

    11 nominal_datatype 'a Maybe = 

    13   Nothing 

    12   Nothing 

    14 | Just 'a

    13 | Just 'a

    15 

    14