is-special-index := (: BTreeEqEOF BTreeEq<Tuple<String,Type>,U64>);

mark-as-special := λ(: name String)(: tt Type). (: (
   (.bind( (as (& is-special-index) BTreeEq<Tuple<String,Type>,U64>[]) (Tuple( name tt )) 1_u64 ))
) Nil);

is-special := λ(: name String)(: tt Type). (: (
   (let r (.lookup( is-special-index (Tuple( name tt )) 0_u64 )))
   r
) U64);