cheat sheets.

XPath examples
==============
//hr[@class='edge' and position()=1]
    every first hr of 'edge' class

//table[count(tr)=1 and count(tr/td)=2]
    all tables with 1 row and 2 cols

//div/form/parent::*
    all divs that have form

./div/b
    a relative path

//table[parent::div[@class="pad"] and not(@id)]//a
    any anchor in a table without id, contained in a div of "pad" class

/html/body/div/*[preceding-sibling::h4]
    give me whatever after h4

//tr/td[font[@class="head" and text()="TRACK"]]
    all td that has font of a "head" class and text "TRACK"

./table/tr[last()]
    the last row of a table

//rdf:Seq/rdf:li/em:id
    using namespaces

//a/@href
    hrefs of all anchors

//*[count(*)=3]
    all nodes with 3 children

//var|//acronym
    all vars and acronyms

XPath functions
===============
Conversion:
    boolean([object])
    string([object])
    number([object])

Math:
    ceiling(number)
    floor(number)
    round(decimal)
    sum(node-set)

Logic:
    true()
    false()
    not(expr)

Node:
    lang(string)
    name([node-set])
    namespace-uri([node-set])
    text()

Context:
    count(node-set)
    function-available(name)
    last()
    position()

String:
    contains(haystack-string needle-string)
    concat(tring1 string2[stringn]*)
    normalize-space(string)
    starts-with(haystack needle)
    string-length([string])
    substring(string start[length])
    substring-after(haystack needle)
    substring-before(haystack needle)
    translate(string abc XYZ)

XPath Axes
==========
Axes are relations to nodes. Some axes also have shortcuts (in parentheses).

Element axes:
    * ancestor
    * ancestor-or-self
    * attribute (@)
    * child (/)
    * descendant (//)
    * descendant-or-self
    * following
    * following-sibling
    * parent(..)
    * preceding
    * preceding-sibling
    * self (.)

Attribute axis:
    * attribute (@)

Namespace axis:
    * namespace

XPath Syntax Details
====================
Absolute path: /step/step/step/...

Relative path: step/step/step/...

Step: axis::node-test[predicate]
  * axis is optional (default is child)
  * predicate is optional (default is true())

Node-test:
  * a type function (text(), comment(), processing-instruction())
  * node() (always true)
  * the name of an attribute, namespace, or element (depending on axis)

Predicate: nested XPath expression relative to current node (no match == false)

Operators: or, and, =, !=, <=, <, >=, >, +, -, *, div, mod, -(unary), |(union)

Shortcut nitty-gritty:
  * @name means "attribute::name"
  * // means "/descendant-or-self::node()/"
  * . means "self::node()"
  * .. means "parent::node()"
  * [4] (as predicate) means "[position() = 4]"