@(let ([open @litchar{(}]

         [close @litchar{)}])

     @BNF[(list @nonterm{expr}

                @nonterm{id}

                @BNF-seq[open @kleeneplus[@nonterm{expr}] close]

                @BNF-seq[open @litchar{lambda}

                          open @kleenestar[@nonterm{id}] close

                          @nonterm{expr} close]

                @nonterm{val})

          (list @nonterm{val}

                @BNF-alt[@nonterm{number} @nonterm{primop}])

          (list @nonterm{id}

                @elem{any name except for @litchar{lambda}})])

‹expr›

 ::= 

‹id›

  |  

( ‹expr›+ )

  |  

( lambda ( ‹id›* ) ‹expr› )

  |  

‹val›

‹val›

 ::= 

‹number›  |  ‹primop›

‹id›

 ::= 

any name except for lambda