[xmonad] workspaces conditional on host name

19 Sep 2022

      Dear All,

I use XMonad on different machines. The configuration is identical, except for the default workspaces, so I'd like to have the config file set the default workspaces automagically. Haskell ignorant here, but googling around I think I am almost there. These are, I think, the relevant pieces

myWorkspaces    = map show[1..7] 
myWorkspacesPhelsuma    = map show[1..3] ++ ["top", "sync", "zot",  "whats"]
myWorkspacesTriturus    = map show[1..2] ++ ["top", "sync"]

main :: IO ()
main = do
   hostname <- io (getEnv "HOSTNAME")
   let myWorkspaces = case hostname of
         "Phelsuma" -> myWorkspacesPhelsuma
         "Triturus" -> myWorkspacesTriturus
         _ -> myWorkspaces
   xmonad
      $ ewmh
      $ dynamicProjects myProjects
      $ withNavigation2DConfig def
      $ docks
      $ withEasySB (statusBarProp "xmobar ~/.xmonad/.xmobarrc" (pure myXmobarPP)) defToggleStrutsKey
      $ myConfig

myConfig = def {
         --- blablabla
         workspaces =  myWorkspaces
         }

However, I keep getting an error:

    • Couldn't match expected type ‘Maybe String’
                  with actual type ‘[Char]’
    • In the pattern: "Phelsuma"
      In a case alternative: "Phelsuma" -> myWorkspacesPhelsuma
      In the expression:
        case hostname of
          "Phelsuma" -> myWorkspacesPhelsuma
          "Triturus" -> myWorkspacesTriturus
          _ -> myWorkspaces
    |
882 |          "Phelsuma" -> myWorkspacesPhelsuma
    |          ^^^^^^^^^^

(and the same error for the second entry, "Triturus")

This I think should be fairly easy to fix, but I can't find how. I tried writing the case section as

let myWorkspaces = case hostname of
         Just "Phelsuma" -> myWorkspacesPhelsuma
         Just "Triturus" -> myWorkspacesTriturus
         _ -> myWorkspaces

and that does not give me an error, but it seems to ignore the actual hostname and uses the "default" one (the one with workspaces 1 to 7). So I think I am using "Just" incorrectly and possibly also misunderstanding how "let" works in main.

Any suggestions?

Thanks,

-- 
Ramon Diaz-Uriarte
Department of Biochemistry, Lab B-31
Facultad de Medicina
Universidad Autónoma de Madrid 
Arzobispo Morcillo, 4
28029 Madrid
Spain

Phone: +34-91-497-2412

Email: rdiaz02@gmail.com
       r.diaz@uam.es

https://ligarto.org/rdiaz