$\forall$$A$:Type, ${\it eq}$:EqDecider($A$), $x$,$y$:$A$, $v$,$z$:top.
\\[0ex]sqequal(fpf{-}cap(fpf{-}single($x$; $v$); ${\it eq}$; $y$; $z$); if eqof(${\it eq}$)($x$,$y$) then $v$ else $z$ fi )