[xmonad] Beginner problem with XMonad and appending to a list rather than prefixing

[Trey Blancher]

XMonad Community,

After all this time, I'm still just a beginner with XMonad. I only know Haskell
through XMonad, and I wouldn't say I know it well. I learn just enough to get
my XMonad configuration to work, then don't return to it for a while.

I'm trying to make a minor change to my XMonad file, where a new
workspace is appended to the list rather than prefixed like I have now,
but I can't seem to figure out the code to do it. Here's the relevant
details of what I have:

import XMonad.Actions.DynamicWorkspaces as DW
import qualified XMonad.Util.ExtensibleState as XS
import Control.Applicative
filterWorkspaces :: [WorkspaceId] -> [WindowSpace] -> [WindowSpace]
filterWorkspaces ws = filter (\(W.Workspace tag _ _) -> tag `elem` ws)
-- xScreen are the type classes which hold the workspace name lists
newtype LeftScreen = LeftScreen {getLeftScreen :: [WorkspaceId]} deriving (Typeable,Read,Show)
instance ExtensionClass LeftScreen where
initialValue = LeftScreen []
extensionType = PersistentExtension


newtype RightScreen = RightScreen {getRightScreen :: [WorkspaceId]} deriving (Typeable,Read,Show)
instance ExtensionClass RightScreen where
initialValue = RightScreen []
extensionType = PersistentExtension

-- snip --

main = do
dbus <- D.connectSession
getWellKnownName dbus;
xmonad $ xfceConfig {
workspaces = ["sh","sb","of","wc","ws","wb","cht"]
, terminal = "urxvtc"
-- Goodbye, my sweet, sweet, sloppy focus
, focusFollowsMouse = False
, manageHook = manageDocks <+> myManageHook -- <+> manageHook defaultConfig
, layoutHook = avoidStruts $ onWorkspace "gimp" gimp $ layoutH
, logHook = dynamicLogWithPP (ppL dbus)

dynamicLogWithPP (ppR dbus)
fadeHook

, borderWidth = 1
, normalBorderColor = "#333333"
, focusedBorderColor = "#CCCC00"
, modMask = winKey
, startupHook = setWMName "LG3D"
} `additionalKeys` myKeys

myKeys = [
-- snip
-- Here's what I want to change
, ((winKey , xK_m) ,DW.withWorkspace myXPConfigNew $ \wk -> do
sc <- screenBy 0
if sc == 0
then XS.modifyf $ LeftScreen . (wk :) . getLeftScreen -- prefix left list with new workspace
--then XS.modify $ LeftScreen . getLeftScreen ++[wk] -- My first attempt at appending the workspace
else XS.modify $ RightScreen . (wk :) . getRightScreen -- prefix right list with new workspace
--else XS.modify $ RightScreen . (wk ++) . getRightScreen -- another attempt
windows $ W.view wk)

Normally I'd ask on #***@irc.freenode.net, but I haven't had time to get on
there. I'm sure this demonstrates my lack of knowledge of XMonad and Haskell in
general, hopefully you can help.

Thanks in advance,

Trey Blancher
***@blancher.net

[Francesco Ariis]

Post by Trey Blancher
I'm trying to make a minor change to my XMonad file, where a new
workspace is appended to the list rather than prefixed like I have now,
but I can't seem to figure out the code to do it. Here's the relevant
[..]

almost!

then XS.modify $ LeftScreen . getLeftScreen . (++ [wk])

^-- this should work.

Haskell is a fun and useful language, if you desire you can learn it
by reading http://learnyouahaskell.com/

[Brandon Allbery]

then XS.modify >nbsp; LeftScreen . getLeftScreen . (++ [wk])

Actually, not quite.

then XS.modify $ LeftScreen . (++ [wk]) . getLeftScreen

(they also asked in IRC and I answered it there, for the record)