Sun Jul  3 08:25:45 UTC 2011  pix@kepibu.org
  * Add support for XMLS-style lists, conflicting with LHTML-style lists
diff -rN -u old-Oh, Ducks!/notes new-Oh, Ducks!/notes
--- old-Oh, Ducks!/notes	2015-09-04 14:25:55.000000000 +0000
+++ new-Oh, Ducks!/notes	2015-09-04 14:25:55.000000000 +0000
@@ -51,7 +51,15 @@
 
 For example,
 : :depends-on (:oh-ducks :closure-html :cxml)
+** Differentiating between LHTML lists and XMLS lists
+While it would, in theory, be possible to inspect lists and determine if they
+are LHTML or XMLS lists, this is not currently done.  You can, however, choose
+which type you'd like to work with by pushing =:lists-are-xmls= or
+=:lists-are-lhtml= to =*features*= before loading "Oh, Ducks!".
 
+Unfortunately, this means you can only expect to use one list type in a single
+lisp image.  Patches to either automagically detect the list type, or to provide
+layered functions are welcome.
 * Usage
 The combination of oh-ducks and closure-html provides an HTML template
 for use with cl-unification, and has the following syntax:
diff -rN -u old-Oh, Ducks!/oh-ducks.asd new-Oh, Ducks!/oh-ducks.asd
--- old-Oh, Ducks!/oh-ducks.asd	2015-09-04 14:25:55.000000000 +0000
+++ new-Oh, Ducks!/oh-ducks.asd	2015-09-04 14:25:55.000000000 +0000
@@ -32,11 +32,17 @@
   :requires (:oh-ducks :closure-html)
   :components ((:file "chtml")
                (:module "traversal"
-                :components ((:file "lhtml")
+                :components (#-lists-are-xmls (:file "lhtml")
                              (:file "pt")))))
 
 (defsystem-connection ducks+cxml
   :requires (:oh-ducks :cxml)
   :components ((:file "cxml")
                (:module "traversal"
-                :components ((:file "dom")))))
+                :components ((:file "dom")
+                             #-lists-are-lhtml (:file "xmls")))))
+
+;; In case you're wondering, we check the inverse of the :lists-are-* keywords
+;; so, in the event you only load cxml (or chtml), and don't specify which
+;; format lists are expected to take, you get the appropriate list operation by
+;; default.
diff -rN -u old-Oh, Ducks!/traversal/xmls.lisp new-Oh, Ducks!/traversal/xmls.lisp
--- old-Oh, Ducks!/traversal/xmls.lisp	1970-01-01 00:00:00.000000000 +0000
+++ new-Oh, Ducks!/traversal/xmls.lisp	2015-09-04 14:25:55.000000000 +0000
@@ -0,0 +1,58 @@
+;;; WARNING: This conflicts with lhtml.
+(in-package #:oh-ducks.traversal)
+
+(defvar *xmls-family-tree* nil)
+
+(defun in-hash (key hash)
+  (multiple-value-bind (val present-p) (gethash key hash)
+    (declare (ignore val))
+    present-p))
+
+(defun %mark-parents (parent children)
+  (dolist (item children)
+    (setf (gethash item *xmls-family-tree*) parent)
+    (%mark-parents item (element-children item))))
+
+;; WARNING: This won't produce sane results for nested (match)es, because we
+;;          have no way to bind in a large enough scope.
+(defmethod unify:unify ((template oh-ducks::css-selector-template)
+                        (element list)
+                        &optional (env (unify:make-empty-environment))
+                        &key)
+  (if (and *xmls-family-tree*
+	   (in-hash element *xmls-family-tree*))
+      (call-next-method)
+      (let ((*xmls-family-tree* (make-hash-table :test 'eq)))
+        (%mark-parents nil (list element))
+        (%mark-parents element (element-children element))
+        (call-next-method))))
+
+(defmethod unify:unify ((document list) (template oh-ducks::css-selector-template)
+                        &optional (env (unify:make-empty-environment))
+                        &key)
+  (unify:unify template document env))
+
+;;; general accessors
+
+(defmethod element-children ((element list))
+  (remove-if-not (lambda (x) (and (listp x) (stringp (car x))))
+                 (cddr element)))
+
+(defmethod element-parent ((element list))
+  (multiple-value-bind (parent present?)
+      (gethash element *xmls-family-tree*)
+    (if present?
+        parent
+        (error "unable to determine parent"))))
+
+#+(or)
+(defmethod element-attribute ((attribute symbol) (element list))
+  (cadr (assoc attribute (cadr element))))
+(defmethod element-attribute ((attribute string) (element list))
+  (cadr (assoc attribute (cadr element) :test #'string=)))
+
+(defmethod element-type ((element list))
+  (car element))
+
+(defmethod element-content ((element list))
+  (cddr element))