On 17 May 2016, at 10:47, 'Simon Brooke' via Clojure <clojure@googlegroups.com>
wrote:
> I'm having trouble with writing a function
> in idiomatic clojure
> which doesn't blow the stack
> The problem is I have a time series of events e.g.
>
> ({:idhistory 78758272, :timestamp #inst
> "2016-03-31T19:34:27.313000000-00:00", :nameid 5637, :stringvalue nil, :value
> 8000.0}
> {:idhistory 78756591, :timestamp #inst
> "2016-03-31T19:33:31.697000000-00:00", :nameid 5637, :stringvalue nil, :value
> 7368.0}
> {:idhistory 78754249, :timestamp #inst
> "2016-03-31T19:32:17.100000000-00:00", :nameid 5637, :stringvalue nil, :value
> 6316.0}
> {:idhistory 78753165, :timestamp #inst
> "2016-03-31T19:31:41.843000000-00:00", :nameid 5637, :stringvalue nil, :value
> 5263.0}
> {:idhistory 78751187, :timestamp #inst
> "2016-03-31T19:30:36.213000000-00:00", :nameid 5637, :stringvalue nil, :value
> 4211.0}
> {:idhistory 78749476, :timestamp #inst
> "2016-03-31T19:29:41.363000000-00:00", :nameid 5637, :stringvalue nil, :value
> 3158.0} ...)
>
> which is to say, each event is a map, and each event has two critical keys,
> :timestamp and :value. The series is sorted in descending order by timestamp,
> i.e. most recent event first. These series are of up to millions of events;
> the average length of the series is about half a million events. However,
> many contain successive events at which the value does not change, and where
> the value doesn't change I want to retain only the first event.
One way of solving this sort of problem without blowing the stack is to use
recur:
https://clojuredocs.org/clojure.core/recur.
I would guess this is the best fit for what you want to do.
Alan
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