Always return a list

[Johan Andersson]

Hey,

I have a struct. To make it simple, lets assume this is the struct:

  (defstruct package name deps)

The deps slot is for the package dependencies. Example of packages:

  (make-package :name "one" :deps "two")

  (make-package :name "two" :deps '("three" "four"))

To make it easier to use the dependencies from the code, when I call (package-deps package) I always want it to return a list. So:

  (let ((one (make-package :name "one" :deps "two"))

        (two (make-package :name "two" :deps '("three" "four"))))

    (print (package-deps one)) ;; => ("two")

    (print (package-deps two)) ;; => ("three" "four")

    )

I tried doing this using an advice, with no success:

  (defadvice package-deps (around package-deps-around)

    (let ((deps ad-do-it))

      (if (listp deps) deps (list deps))))

  (ad-activate 'package-deps)

Can I do this in a way that doesn't require that much of a hack?

Thanks!