'XMonad.Actions.SwapPromote': 'stackMerge' fixes

Make 'stackMerge' safer by implicitly appending any leftover elements
rather than discarding them. Otherwise on refresh the missing windows
will be deleted. This is only necessary if the stack has been shortened
- i.e. not required by this module.

Minor miscellaneous documentation fixes.

XMonad/Actions/SwapPromote.hs

@@ -106,6 +106,7 @@ import           Control.Monad
 -- windows will be ignored.
 --
 -- All together:
+--
 -- > , ((mod1Mask, xK_Return), whenX (swapHybrid True) dwmpromote)
 
 
@@ -315,18 +316,20 @@ cycleN n ls =
     let l = length ls
     in  take l $ drop (n `mod` l) $ cycle ls
 
--- Wrap 'split'' with an initial index of @0@, discarding the list's length.
+-- | Wrap 'split'' with an initial index of @0@, discarding the list's length.
 split :: (Num a, Enum a) => (b -> Bool) -> [b] -> ([(a,b)],[b])
 split p l =
     let (_,ys,ns) = split' p 0 l
     in  (ys,ns)
 
--- Given a predicate, an initial index and a list, return a tuple containing:
+-- | Given a predicate, an initial index and a list, return a tuple containing:
+--
 --  * List length.
 --  * Indexed list of elements which satisfy the predicate. An indexed element
 --    is a tuple containing the element index (offset by the initial index) and
 --    the element.
 --  * List of elements which do not satisfy the predicate.
+--
 -- The initial index and length of the list simplify chaining calls to this
 -- function, such as for zippers of lists.
 split' :: (Num a, Enum a) => (b -> Bool) -> a -> [b] -> (a,[(a,b)],[b])
@@ -337,17 +340,18 @@ split' p i l =
         (c',ys',ns') = foldr accumulate (0,[],[]) $ zip [i..] l
     in  (c',ys',snd . unzip $ ns')
 
--- Wrap 'merge'' with an initial virtual index of @0@. Return only the
+-- | Wrap 'merge'' with an initial virtual index of @0@. Return only the
 -- unindexed list with elements from the leftover indexed list appended.
 merge :: (Ord a, Num a) => [(a,b)] -> [b] -> [b]
 merge il ul =
     let (_,il',ul') = merge' 0 il ul
     in  ul' ++ map snd il'
 
--- Inverse of 'split'. Merge an indexed list with an unindexed list (see
+-- | Inverse of 'split'. Merge an indexed list with an unindexed list (see
 -- 'split''). Given a virtual index, an indexed list and an unindexed list,
 -- return a tuple containing:
---  * Virtual index *after* the unindexed list
+--
+--  * Virtual index /after/ the unindexed list
 --  * Remainder of the indexed list
 --  * Merged unindexed list
 --
@@ -391,10 +395,10 @@ stackSplit (W.Stack x l r) s =
 
 -- | Inverse of 'stackSplit'. Given a list of elements and their original
 -- indices, re-insert the elements into these same positions within the stack.
--- Skip the currently focused member.  Works best if the stack's length hasn't
+-- Skip the currently focused member. Works best if the stack's length hasn't
--- changed. Some elements may be excluded if shorter.
+-- changed, though if shorter any leftover elements will be tacked on.
 stackMerge :: (Ord a, Num a) => W.Stack b -> [(a,b)] -> W.Stack b
 stackMerge (W.Stack x l r) il =
     let (i,il1,l') = merge' 0 il (reverse l)
-        (_,_  ,r') = merge' (i+1) il1 r
+        (_,il2,r') = merge' (i+1) il1 r
-    in  W.Stack x (reverse l') r'
+    in  W.Stack x (reverse l') (r' ++ map snd il2)