(VAR x y z u v)
(RULES
merge(nil,y) -> y
merge(x,nil) -> x
merge(.(x,y),.(u,v)) -> if(<(x,u),.(x,merge(y,.(u,v))),.(u,merge(.(x,y),v)))
++(nil,y) -> y
++(.(x,y),z) -> .(x,++(y,z))
if(true,x,y) -> x
if(false,x,y) -> x
)

(COMMENT Example 2.43 in \cite{SK90})