Contextual functions can only be used when the context is known
Determines the location of an element in the document.
Takes a selector that must match exactly one element and returns that
element's location. This location can, in particular, be used to
retrieve the physical page number and
position (page, x, y) for that element.
Examples
Locating a specific element:
#context[
Introduction is at: \#locate(<intro>).position()]= Introduction<intro>
Parameters
Parameters are the inputs to a function. They are specified in
parentheses after the function name.