[xmonad] How to organize myLayoutHook?

[Daniel Trstenjak]

On Wed, Oct 17, 2012 at 09:13:25AM -0700, Jeffrey David Johnson wrote:
> xmonad.hs:43:40:
>     Couldn't match type `XMonad.Layout.LayoutModifier.ModifiedLayout
>                            XMonad.Layout.Renamed.Rename FixedColumn'
>                   with `Full'
>     Expected type: Full a0
>       Actual type: XMonad.Layout.LayoutModifier.ModifiedLayout
>                      XMonad.Layout.Renamed.Rename FixedColumn a0
>     In the first argument of `(|||)', namely `tall'
>     In the expression: tall ||| wide
>     In the expression: ("notes", "~/notes", tall ||| wide)
> 

I think that's the case, because you can't put different layout types - regardless if
they all have an instance of the same type class (LayoutClass) - in the same list,
without the usage of existential quantification.


I tried this:

data AnyLayout a = forall l. (LayoutClass l a) => AnyLayout (l a)

test = format [("admin", "~/dotfiles", AnyLayout $ Tall 1 (3/100) (2/3)),
               ("notes", "~/notes"   , AnyLayout $ Full)]
   where
      defaultWorkspace = dragPane Vertical 0.1 0.5

      format (w:[]) = workspace w $ defaultWorkspace
      format (w:ws) = workspace w $ format ws

      workspace (name, dir, AnyLayout l) = onWorkspace name l $ modWorkspace name (workspaceDir dir)


But this still results in some compile error, and I don't even know, if
it's possible to use existential quantification here.


xmonad.hs:79:8:
    No instance for (LayoutClass
                       ((->) (l0 a0))
                       (PerWorkspace
                          (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l0)
                          l0
                          a0))
      arising from a use of `format'
    Possible fix:
      add an instance declaration for
      (LayoutClass
         ((->) (l0 a0))
         (PerWorkspace
            (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l0)
            l0
            a0))
    In the expression:
      format
        [("admin", "~/dotfiles", AnyLayout $ Tall 1 (3 / 100) (2 / 3)),
         ("notes", "~/notes", AnyLayout $ Full)]
    In an equation for `test':
        test
          = format
              [("admin", "~/dotfiles", AnyLayout $ Tall 1 (3 / 100) (2 / 3)),
               ("notes", "~/notes", AnyLayout $ Full)]
          where
              defaultWorkspace = dragPane Vertical 0.1 0.5
              format (w : []) = workspace w $ defaultWorkspace
              format (w : ws) = workspace w $ format ws
              workspace (name, dir, AnyLayout l)
                = onWorkspace name l $ modWorkspace name (workspaceDir dir)

xmonad.hs:87:44:
    Could not deduce (t1
                      ~ PerWorkspace
                          l1
                          ((->) (l a))
                          (PerWorkspace
                             (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l) l a))
    from the context (LayoutClass l a,
                      LayoutClass
                        ((->) (l a))
                        (PerWorkspace
                           (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l) l a))
      bound by the inferred type of
               workspace :: (LayoutClass l a,
                             LayoutClass
                               ((->) (l a))
                               (PerWorkspace
                                  (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l)
                                  l
                                  a)) =>
                            ([Char],
                             [Char],
                             AnyLayout
                               (PerWorkspace
                                  (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l) l a))
                            -> t1
      at xmonad.hs:87:7-100
    or from (LayoutClass
               l1
               (PerWorkspace
                  (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l) l a))
      bound by a pattern with constructor
                 AnyLayout :: forall a (l :: * -> *).
                              LayoutClass l a =>
                              l a -> AnyLayout a,
               in an equation for `workspace'
      at xmonad.hs:87:29-39
      `t1' is a rigid type variable bound by
           the inferred type of
           workspace :: (LayoutClass l a,
                         LayoutClass
                           ((->) (l a))
                           (PerWorkspace
                              (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l)
                              l
                              a)) =>
                        ([Char],
                         [Char],
                         AnyLayout
                           (PerWorkspace
                              (XMonad.Layout.LayoutModifier.ModifiedLayout WorkspaceDir l) l a))
                        -> t1
           at xmonad.hs:87:7
    In the expression:
      onWorkspace name l $ modWorkspace name (workspaceDir dir)
    In an equation for `workspace':
        workspace (name, dir, AnyLayout l)
          = onWorkspace name l $ modWorkspace name (workspaceDir dir)
    In an equation for `test':
        test
          = format
              [("admin", "~/dotfiles", AnyLayout $ Tall 1 (3 / 100) (2 / 3)),
               ("notes", "~/notes", AnyLayout $ Full)]
          where
              defaultWorkspace = dragPane Vertical 0.1 0.5
              format (w : []) = workspace w $ defaultWorkspace
              format (w : ws) = workspace w $ format ws
              workspace (name, dir, AnyLayout l)
                = onWorkspace name l $ modWorkspace name (workspaceDir dir)


Greetings,
Daniel