Bug with interval difference

[malcolmsparks]

(t/difference
 [(t/new-interval (t/in (t/date-time "2020-02-01T00:00") juxt.time/LONDON)
                  (t/in (t/date-time "2020-02-02T00:00") juxt.time/LONDON))
  (t/new-interval (t/in (t/date-time "2020-02-02T00:00") juxt.time/LONDON)
                  (t/in (t/date-time "2020-02-03T00:00") juxt.time/LONDON))
  (t/new-interval (t/in (t/date-time "2020-02-03T00:00") juxt.time/LONDON)
                  (t/in (t/date-time "2020-02-04T00:00") juxt.time/LONDON))
  ]
 [
  (t/new-interval (t/in (t/date-time "2020-02-01T12:00") juxt.time/LONDON)
                  (t/in (t/date-time "2020-02-03T12:00") juxt.time/LONDON))
  ]
 
 )

gives

(#:tick{:beginning
        #time/zoned-date-time "2020-02-01T00:00Z[Europe/London]",
        :end
        #time/zoned-date-time "2020-02-01T12:00Z[Europe/London]"}
 #:tick{:beginning
        #time/zoned-date-time "2020-02-03T00:00Z[Europe/London]",
        :end
        #time/zoned-date-time "2020-02-04T00:00Z[Europe/London]"})

[t-taylor]

(t/difference
  [(t/new-interval (t/date-time "2020-02-01T00:00")
                   (t/date-time "2020-02-02T00:00"))]
  [(t/new-interval (t/date-time "2020-02-01T00:00")
                   (t/date-time "2020-02-02T12:00"))])

returns

;; => ()

[t-taylor]

;; X |-------------------|
;; Y |----------|
;; should be :started-by, return :starts
(t/relation
  (t/new-interval (t/date-time "2020-02-01T00:00")
                  (t/date-time "2020-02-02T00:00"))
  (t/new-interval (t/date-time "2020-02-01T00:00")
                  (t/date-time "2020-02-02T12:00")))

[malcolmsparks]

Very nice spot! If you have time, please send on a PR. This bug has derailed some time calculation I wanted to complete.

[t-taylor]

This isn't right actually :/ the example has a typo on the 2nd interval, so Y ends later than X. This part works correctly. It is to do with chuncking the intervals instead

[t-taylor]

;; X     |-----|-----|
;; Y  |-----------|
;;=>           |-----|
;; (broken)
(t/difference
  [(t/new-interval (t/date-time "2020-02-02T00:00")
                   (t/date-time "2020-02-03T00:00"))
   (t/new-interval (t/date-time "2020-02-03T00:00")
                   (t/date-time "2020-02-04T00:00"))]
  [(t/new-interval (t/date-time "2020-02-01T00:00")
                   (t/date-time "2020-02-03T12:00"))])

;; X     |-----|-----|
;; Y     |--------|
;;=>              |--|
;; (works)
(t/difference
  [(t/new-interval (t/date-time "2020-02-02T00:00")
                   (t/date-time "2020-02-03T00:00"))
   (t/new-interval (t/date-time "2020-02-03T00:00")
                   (t/date-time "2020-02-04T00:00"))]
  [(t/new-interval (t/date-time "2020-02-02T00:00")
                   (t/date-time "2020-02-03T12:00"))])

;; Seems problem is when a :during is followed by a :overlapped-by