Not sure what the syntax is, but I agree that holding to a fixed number of arguments will be best, particularly for filtering out syntax errors.

On 17 Nov 2021, at 11:51, phoebe Goldman wrote:

On Nov 17, 2021, at 12:37 PM, Robert Goldman <rpgoldman@sift.info> wrote:

version constraints like (:version "my-unstable-library" < 3) or something like that will go in to ASDF.

Might I suggest the syntax:

(:version "my-lib" (:min "2")) ; equiv to (:version "my-lib" "3")

(:version "my-lib" (:below "3")) ; not :MAX, because this is an exclusive bound

(:version "my-lib" (:range "2" "3")) ; inclusive lower, exclusive upper bound

I believe it is both useful and aesthetically pleasing to keep the :version form to exactly three elements.

cheers,

phoebe