// deleted concrete syntax (" ... ") and pretty-print commands ( *s and *l)
// and implements 
Main =   <cd> ClassDefList .

ClassDef =  <name> Ident  <decl> Decl  .
Decl: Abstract | Concrete.
Abstract =   <subtypes> NESubtypeList.
Concrete =   <fields> FieldList.

Field =  <name> Ident   <typename> TypeName.
TypeName = <name> Ident.

ClassDefList: ClassDefCons | ClassDefEmpty.
ClassDefCons = <first> ClassDef <rest> ClassDefList. // implements ConsList.
ClassDefEmpty =  . // implements EmptyList.

FieldList: FieldCons | FieldEmpty.
FieldCons = <first> Field  <rest> FieldList. // implements ConsList.
FieldEmpty =  . // implements EmptyList.

NESubtypeList = <first> TypeName <rest> SubtypeList. // implements ConsList.
SubtypeList: SubtypeCons | SubtypeEmpty.
SubtypeCons =   <first> TypeName <rest> SubtypeList. // implements ConsList.
SubtypeEmpty = . // implements EmptyList.

// noparse

// interface ConsList = .
// interface EmptyList = .