There are a few concepts to get familiar with before getting to grips with kantan.xpath proper.

Regular expression literals

First, xpath literals: xpath expressions that are validated at compile time. This is the preferred way of creating xpath expressions and will be used throughout the documentation, so it’s best to get that out of the way as soon as possible.

There are various ways of enabling the feature, the simplest and most common one being to import kantan.xpath.implicits._:

import kantan.xpath.implicits._

This will also bring kantan.xpath syntax in scope though, so if you only want the literals, you can simply import kantan.xpath.literals._.

This lets you create new regular expression by prefixing string literals with xp:

// res0: kantan.xpath.package.XPathExpression = kantan.xpath.XPathCompiler$$anon$2@71e3f412

And, as promised, this fails at compile time if the xpath expression is not valid:

// error: Illegal XPath expression: '!@#'
// xp"!@#"
// ^^^^^^^

Simple evaluation

Subsequent pages will get into more details, but the simplest, most idiomatic way of extracting well typed data from strings using kantan.xpath is through the evalXPath method that enriches strings (since we’ve imported kantan.xpath.implicits._).

For example, retrieving only the first match:

"<users><user id='1'/><user id='2'/></users>".evalXPath[Int](xp"//user/@id")
// res2: kantan.xpath.package.XPathResult[Int] = Right(value = 1)

And retrieving all matches:

"<users><user id='1'/><user id='2'/></users>".evalXPath[List[Int]](xp"//user/@id")
// res3: kantan.xpath.package.XPathResult[List[Int]] = Right(
//   value = List(1, 2)
// )

Other tutorials: