define-xpath-function/eager (ext name args &body body)

Defines an XPath function, "eager" style.

The body is evaluated during evaluation of XPath expressions each time the function being defined is called. It's passed a list of values corresponding to XPath function arguments and should return a value of one of XPath types (string, boolean, number, node set).

Example:

   (define-xpath-function/eager my-ext join (delim node-set)
     (reduce (lambda (a b) (concatenate 'string a delim b))
             (map-node-set->list #'string-value node-set)))