diff options
| -rw-r--r-- | StackSet.hs | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/StackSet.hs b/StackSet.hs index e57e80e..f4f482d 100644 --- a/StackSet.hs +++ b/StackSet.hs @@ -302,11 +302,16 @@ differentiate (x:xs) = Just $ Stack x [] xs -- /O(n)/. 'filter p s' returns the elements of 's' such that 'p' evaluates to -- True. Order is preserved, and focus moves to the next node to the right (if -- necessary). +-- +-- Note, this isn't the same as the 'remove' semantics, as focus +-- won't move 'left' on the end of list. +-- filter :: (a -> Bool) -> Stack a -> StackOrNot a -filter p (Stack f ls rs) = Just $ case L.filter p (f:rs) of - (f':rs') -> Stack f' (L.filter p ls) rs' - _ -> Stack f' [] rs' - where (f':rs') = reverse (L.filter p ls) +filter p (Stack f ls rs) = case L.filter p (f:rs) of + f':rs' -> Just $ Stack f' (L.filter p ls) rs' -- maybe move focus down + [] -> case L.filter p (reverse ls) of -- filter back up + f':rs' -> Just $ Stack f' [] rs' -- else up + [] -> Nothing -- | -- /O(s)/. Extract the stack on the current workspace, as a list. |