v1		input view 1
r1		input row 1
v2		input view 2
r2		input row 2

Rowcmp returns a value -1, 0, or 1, depending on whether v1/r1 is less, equal, or greater than v2/r2, respectively.

set v [view {A B} def {1 2 3 4 1 2}]

view $v rowcmp 0 $v 1

-1

view $v rowcmp 0 $v 2

0