Operation error in problem definition

General Discussion
21

I found the method for Newton method implemented in the example

https://www.ljll.math.upmc.fr/hecht/ftp/ff++/2018-XVIII-las-Palmas/edp-XVIII/04Rayleigh-Benard.edp

is much more better than the example mentioned in

https://www.um.es/freefem/ff++/pmwiki.php?n=Main.Newton2