chickadee » sxpath » txpath

Returns a procedure that accepts an SXML document tree and an optional association list of variable bindings and returns a nodeset (list of nodes) that match the XPath expression string.

The optional ns-binding argument is an alist of namespace bindings. It is used to map abbreviated namespace prefixes to full URI strings.

(txpath x) is equivalent to (sxpath x) whenever x is a string. The txpath, sxml:xpath+root and sxml:xpath+root+vars procedures are currently all aliases for sxml:xpath, which exist for backwards compatibility reasons.

It's useful to compare the following examples to the above examples for sxpath.

(use txpath)

;; selects all the 'item' elements that have an 'olist' parent
;; (which is not root) and that are in the same document as the context node
((txpath "//olist/item")
 '(doc (olist (item "1")) (item "2") (nested (olist (item "3")))))
 => ((item "1") (item "3"))

;; Same example as above, but now with a namespace prefix of 'x',
;; which is bound to the namespace "bar" in the ns-binding parameter.
((txpath "//x:olist/item" '((x . "bar")))
 '(doc (bar:olist (item "1")) (item "2") (nested (olist (item "3")))))
 => ((item "1"))


(use sxpath sxpath-lolevel data-structures)

;; selects only the nth 'item' element under each 'olist' parent
;; (which is not root) and that is in the same document as the context node
;; The n is parameterized to be the first item
((txpath "//olist/item[$n]")
 '(doc (olist (item "1") (item "2")) (nested (olist (item "3")))) '((n . 1)))
 => ((item "1") (item "3"))

;; selects the 'chapter' children of the context node that have one or
;; more 'title' children with string-value equal to 'Introduction'
((txpath "chapter[title='Introduction']")
 '(text  (chapter (title "Introduction"))  (chapter "No title for this chapter")  (chapter (title "Conclusion"))))
 => ((chapter (title "Introduction")))