<PRIVATE
-: first-unsafe ( seq -- first )
- 0 swap nth-unsafe ; inline
+: first-unsafe ( seq -- first ) 0 swap nth-unsafe ; inline
+: second-unsafe ( seq -- second ) 1 swap nth-unsafe ; inline
+: third-unsafe ( seq -- third ) 2 swap nth-unsafe ; inline
+: fourth-unsafe ( seq -- fourth ) 3 swap nth-unsafe ; inline
: first2-unsafe ( seq -- first second )
- [ first-unsafe ] [ 1 swap nth-unsafe ] bi ; inline
+ [ first-unsafe ] [ second-unsafe ] bi ; inline
: first3-unsafe ( seq -- first second third )
- [ first2-unsafe ] [ 2 swap nth-unsafe ] bi ; inline
+ [ first2-unsafe ] [ third-unsafe ] bi ; inline
: first4-unsafe ( seq -- first second third fourth )
- [ first3-unsafe ] [ 3 swap nth-unsafe ] bi ; inline
+ [ first3-unsafe ] [ fourth-unsafe ] bi ; inline
: exchange-unsafe ( m n seq -- )
[ [ nth-unsafe ] curry bi@ ]