MACRO:: row>tuples ( spec -- quot )
    0 :> i!
    spec [
        unclip :> ( setters tuple-class )
        [
            tuple-class , \ new ,
            setters [ i , \ pick , \ nth-unsafe , , i 1 + i! ] each
            \ , ,
        ] [ ] make
    ] map [ ] concat-as '[ _ { } make nip ] ;

MACRO: rows>tuples ( spec -- quot )
    '[ [ _ row>tuples ] map ] ;


TUPLE: bag id beans ;
TUPLE: bean id color ;

{ { 0 0 "blue" } { 0 1 "red" } }
{ { bag >>id } { bean >>id >>color } } rows>tuples .

{
    { T{ bag { id 0 } } T{ bean { id 0 } { color "blue" } } }
    { T{ bag { id 0 } } T{ bean { id 1 } { color "red" } } }
}