Convert the modified cursors back to a document

I want to use the haskell module Text.XML.Cursor to parse a xml document.

First I convert the document to cursors with fromDocument, then apply some filter. Now I want to get the document back. I think there should be a toDocument function, but it appears no. How can I Convert the modified cursors back?

Here's a filterDocument function that should do what you want:

import Text.XML (Document(..), Node(..))
import Text.XML.Cursor (Cursor, fromDocument, node)

filterDocument :: (Cursor -> Cursor) -> Document -> Maybe Document
filterDocument f doc = case node (f (fromDocument doc)) of
    NodeElement root -> Just doc{ documentRoot = root }
    _ -> Nothing

I basically just looked at the definition of the fromDocument function and inverted what it did. Two notes:

1. It needs the original Document because fromDocument discards the prologue and epilogue.
2. It returns its result in a Maybe because the Cursor you return might point to a non-element node (e.g., a comment or text node), but an XML document needs an element as the root.