As operations on dynamic function references become more complex, and since
evolution of the reference structure is planned to evolve, maintaining an
abstraction is vital for both grokking and maintenance.
Previously, a separate `@partial' attribute was added to the ref and the
`@arity' maintained. Unfortunately, this coupled `f:arity' with
`f:partial', which is unnecessary, considering that partial application is
supposed to conceptually yield a new function, which should be transparent
to `f:arity'.
I am aware of the Saxon 9 warning regarding multiple imports of arity.xsl;
I'm going to choose to ignore this, formally in the future. Each of the
stylesheets is treated like a module.
Michael Kay, Saxon's author, discusses it here:
http://stackoverflow.com/a/10102298