Columnz challenge in Factor

columnz.factor

USING: kernel locals sequences ;
IN: columnz

:: all-equal-first? ( col -- ? )
    col [ col first = ] all? ;

: sum-or-first ( seq -- n )
    dup all-equal-first? [ first ] [ sum ] if ;

: sum-or-first-seq ( seq -- seq )
    flip [ sum-or-first ] map ;