[ dup length ] unless* tail-slice ; inline
: join-with ( seq glue -- newseq )
- V{ } clone [
- [ '[ _ _ push ] ] [ '[ _ push ] ] bi interleave
- ] keep { } like ;
+ [ dup length dup 1 - + 0 max ] dip <array>
+ [ '[ 2 * _ set-nth-unsafe ] each-index ] keep ;