Hi Basile, I think that the error you get comes from a transition from opam1 (used in the Patoline webpage for instructions, I guess) to opam2, which changed the "opam switch" behavior to stop installing a new switch explicitly. The command recommended in the error message, "opam switch create 4.05.0", will do the equivalent of the README's command, and get you a 4.05.0 switch. You should be able to build Patoline there, assuming the dependency bounds have not bitrotted away. Getting Patoline to work on a more recent OCaml version may be very easy (just installing it in a newer switch) or very hard, depending on the change-robustness and maintenance level of its codebase and various dependencies. You cannot tell without trying. Looking at the "issues" list suggests that Patoline is intermittently maintained by Rodolphe Lepigre, so I think you should get help if you open an issue on the repository to report on any further trouble installing Patoline, using either 4.05 or a more recent version. On Tue, Feb 23, 2021 at 11:32 AM Basile Starynkevitch < basile@starynkevitch.net> wrote: > Hello all, > > > I am interesting in compiling the PatoLine typesetting system on some > Ubuntu 20.04 desktop > > (either Intel Xeon Silver 4114 at work, or AMD Ryzen Threadripper 2970WX > at home; with at least 64Gbytes of RAM, and plenty of disk space) > > PatoLine is on https://github.com/patoline/patoline > > I would like to use a rather recent Ocaml (4.08 or newer) > > With the git commit 3dcd41fdff6489 of PatoLine I am getting > > rimski% opam switch 4.05.0 > [ERROR] No switch 4.05.0 is currently installed. Did you mean 'opam > switch create > 4.05.0'? > Installed switches are: > - default > > Thanks for help > > > -- > Basile Starynkevitch > (only mine opinions / les opinions sont miennes uniquement) > 92340 Bourg-la-Reine, France > web page: starynkevitch.net/Basile/ > >