Modifying constructor for span structures.
(change-span x [:start <start>] [:end <end>])
This is an often useful alternative to make-span.
We construct a new span structure that is a copy of
This is an ordinary
Macro:
(defmacro change-span (x &rest args) (std::change-aggregate 'span x args '((:start . span->start) (:end . span->end)) 'change-span 'nil))