first2 swapd remove 2array ;
: combine-stacks ( stacks -- stack )
- [ first first ] [ [ second ] map sets:combine ] bi 2array ;
+ [ first first ] [ [ second ] map sets:union-all ] bi 2array ;
: classify-read ( stack n -- val )
swap 2dup second member? [ 2drop 2 ] [ first >= [ 1 ] [ 0 ] if ] if ;