`plus` is not commutative

[p-himik]

(jt/plus  (jt/zoned-date-time) (jt/minutes 1))
=> #inst"2019-04-06T10:35:04.615-00:00"
(jt/plus (jt/minutes 1) (jt/zoned-date-time))
Execution error (ClassCastException) at java-time.amount/d-plus (amount.clj:12).
class java.time.ZonedDateTime cannot be cast to class java.time.Duration (java.time.ZonedDateTime and java.time.Duration are in module java.base of loader 'bootstrap')

[dm3]

Should plus be commutative though? What do you think should be the laws of algebra involving all of the date-times, intervals and periods?

Currently the API follows the Java object model where the date/time always comes first when a period/duration is added/subtracted. In Java this happens naturally due to the placement of methods. In Clojure we can do as we like. However, date-times and durations are different types - it's not obvious that operations including both should be commutative. Maybe the plus/minus naming could be changed to something like add-duration or extend to clear up the behaviour (although I quite like plus), what do you think?

[p-himik]

To be honest, I didn't really give it much thought so I cannot answer your questions properly. It's very well possible that the current state of affairs is the best one. It was just not really intuitive for me (at first, I even started searching in a completely different direction), and I didn't find any previous discussions on the matter.
If all is fine as it is, the issue can be closed and left just as a documentation for someone with a similar concern.

[dm3]

Added a j/plus API comment.