XPath Functions

The XPath specs define a number of useful functions which are specific to XML, other string or number related functionality is provided by Scala itself and is not replicated by the XPath DSL.

Organisation

The XPath Functions are organised into two main type classes:

1. Names
2. TextValue
3. Boolean

Names provides a type class for any type that can represent a QName:

• Attributes
• Elems
• XmlTrees
• XPaths (name of the first node, "empty" otherwise)
• QNames

TextValue, representing everything that can produce a text value, has a similar base list:

• XmlTrees
• Attributes
• XmlItems
• XPaths (value of the first node)

In general if any logical combination thereof is possible they are also supported (for example XmlPaths themselves)

The boolean family of type class instances:

• XPaths (is it non-empty)
• Iterables (is it non-empty)
• String (length > 0)
• Number (value > 0)

and of course

• Boolean

QName Functions

The full list of functions is available here.

Some examples:

  val attr : Attribute = "attr" -> "value"

  qname(attr) // attr
  pqName(attr) // {}attr
  namespaceUri(attr) // ""

  val ns = Namespace("uri:namespace")
  val pre = ns.prefixed("pre")

  val prefixedAttr : Attribute = pre("prefixed") -> "prefixed value"
  
  qname(prefixedAttr) // pre:prefixed
  pqName(prefixedAttr) // pre:{uri:namespace}prefixed
  namespaceUri(prefixedAttr) // uri:namespace

  val elem = Elem(pre("prefixedElem"))
  
  qname(elem) // pre:prefixedElem
  pqName(elem) // pre:{uri:namespace}prefixedElem
  namespaceUri(elem) // uri:namespace

  val tree = elem /( elem ~> "\ndeep  value\n" )

  pqName(tree) // pre:{uri:namespace}prefixedElem

Using the `name` function with a non QName XPath (e.g. an XmlItem) will result in an exception.

Text Functions

The full list of functions is available here.

Some examples (using the above definitions):

  value(attr) // value
  value(prefixedAttr) // prefixed value

  // won't compile as there is no meaningful way to get an elems value
  // value(elem)

  value(tree.toTree) // \ndeep  value\n
  normalizeSpace(tree) // deep value, but using type class directly

Boolean Function

  boolean("") // false
  boolean("value") // true

  boolean(true) // true