[ length integer>fixnum-strict ] keep
[ set-nth-unsafe ] [ [ 1 fixnum+fast ] dip length<< ] 2bi ; inline
+: push-all-unsafe ( from to src dst -- )
+ [ over - swap ] 2dip pickd [ length integer>fixnum-strict ] keep
+ [ [ fixnum+fast ] dip length<< ] 2keep <copier> (copy) drop ; inline
+
PRIVATE>
: capacity ( seq -- n ) underlying>> length ; inline