Re: [pro] style question about types, coercion, expectations for function parameters

Ryan Davis ryan@acceleration.net writes:

The answer we arrived at was "yes":

(defun send-email (to from subject body)
  (let ((to (etypecase to
              (string to)
              ((integer 0) (email (fetch-client to)))
              (client (email to))
              )))
    ;; ... more code
    ))

The "to" parameter can be anythings that can be mapped to an email address.

Yes, it's what's usually called a "designator", specifically, an email designator. CL itself defines and uses a few designator types (string designators, package designators, pathname designators, list designators, etc).