Not sure what to call this type of operation.

squeeze.rb

# Input
events = [
  event(status: 'IDLE', job: 1, date: '2014-01-01'),
  event(status: 'BUSY', job: 1, date: '2014-01-02'),
  event(status: 'BUSY', job: 1, date: '2014-01-03'),
  event(status: 'BUSY', job: 2, date: '2014-01-04'),
  event(status: 'BUSY', job: 2, date: '2014-01-05'),
  event(status: 'BUSY', job: 2, date: '2014-01-06'),
  event(status: 'IDLE', job: 2, date: '2014-01-07'),
  event(status: 'BUSY', job: 3, date: '2014-01-08'),
  event(status: 'BUSY', job: 3, date: '2014-01-09'),
  event(status: 'IDLE', job: 3, date: '2014-01-10')
]

# Output
activity_feed = [
  activity(status: 'IDLE', job: 1, date: '2014-01-01'),
  activity(status: 'BUSY', job: 1, date: '2014-01-03'),
  activity(status: 'BUSY', job: 2, date: '2014-01-06'),
  activity(status: 'IDLE', job: 2, date: '2014-01-07'),
  activity(status: 'BUSY', job: 3, date: '2014-01-09'),
  activity(status: 'IDLE', job: 3, date: '2014-01-10')
]

expect {
  build_activity_feed(events)
}.to eql(activity_feed)

# Basically we are folding events with the same status or job starting
# from the right and folding left. I want to call this foldr, but
# descriptions I've found imply fold algorithms convert a vector into a
# scalar. ie. [1,2,3] => 6
#
# Is there a common name for this operation? Squeeze? Compact?