Chris Marusich <cmmarus...@gmail.com> skribis: > Chris Marusich <cmmarus...@gmail.com> writes: > >>> >>> (define (emit-bind-options-config options) >>> (match options >>> (($ <bind-options-configuration> user _ run-directory pid-file >>> listen-v4 listen-v6 listen-port >>> allow-recursion? allow-transfer? >>> allow-update? >>> version hostname server-id) >> >> Some of these slots (e.g., listen-v4) appear to be un-used. Instead of >> listing positional slots by name, maybe it would be better to bind the >> entire <bind-options-configuration> to a variable, and then use the >> accessor procedures (e.g., bind-options-configuration-listen-v4) to get >> just the attributes you need. This has the benefit of being more >> resilient to refactorings which change the order of fields in the >> record, also. I realize that a lot of the code in Guix relies on >> positional matching of slots like this, so I don't mind if you keep it >> as-is, but consider my suggestion as food for thought. > > FYI, I just learned that there is a way to do this with pattern matching > in Guile. You can write something like the following: > > (match options > ((? bind-options-configuration? (= bind-options-configuration-listen-v4 > listen-v4)) > ;; Do something with listen-v4 > (foo listen-v4))) > > As far as I know, this is the same as writing something like: > > (match options > ((? bind-options-configuration? opts) > (let ((listen-v4 (bind-options-configuration-listen-v4 opts))) > ;; Do something with listen-v4 > (foo listen-v4))))
In this particular case I would argue that the second version is more readable. Ludo’.
