在XSLT中，哈希（＃）后面跟一个数字意味着什么？

Question

For example, the #1 in:

f:is-subordinate($M, $E, f:direct-reports#1)

from http://www.w3.org/TR/xslt-30/#d7e22590

Answer 1

This is called the arity, and it's the number of parameters required by a function. If you don't have any hash (#), the arity of the function is 0.

Here, it refers to a direct-reports function which take a single parameter.

With arity, you can have several functions with the same name, but a number of parameters which differs.

Answer 2

The example you point to is a higher-order function that takes another function as a parameter. The f:direct-reports#1 denotes the function named f:direct-reports that takes 1 argument - the number after the hash is referred to as the function's arity - and this function#arity syntax is the way you refer to the function itself as a first-class object, as opposed to calling the function and making use of its return value.