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;; differences from scheme unfold
;; even initial value is lazy
;; predicate sense reversed
;; internal state == produced value, no special mapper-fn
;; no tail-gen
(defn series
"Produces a sequence of values.
`f` is a function that given a value, returns the next value.
`continue?` is a predicate that determines whether to produce
the next value. `f` called with no arguments produces the
initial value. Always produces at least one value."
[f continue?]
(reify
clojure.lang.Seqable
(seq [_]
((fn step [seed]
(cons seed
(when (continue? seed)
(lazy-seq (step (f seed))))))
(f)))
clojure.lang.IReduceInit
(reduce [_ rf init]
(loop [seed (f)
ret (rf init seed)]
(if (reduced? ret)
@ret
(if (continue? seed)
(let [next (f seed)]
(recur next (rf ret next)))
ret))))
clojure.lang.Sequential))
(defn supply
"Produces a sequence of values by repeatedly calling `f` for side-effects
until it returns `fin`. The sequence can be used lazily/caching or
reducible/non-caching. Not guaranteed to produce any values"
[f fin]
(reify
clojure.lang.Seqable
(seq [_]
((fn step []
(let [v (f)]
(if (identical? v fin)
nil
(cons v (new clojure.lang.LazySeq step)))))))
clojure.lang.IReduceInit
(reduce [_ rf init]
(loop [res init]
(let [v (f)]
(if (identical? v fin)
res
(let [res (rf res v)]
(if (reduced? res)
@res
(recur res)))))))
clojure.lang.Sequential))
;; supply
(supply #(or (.readLine ^BufferedReader rdr) ::eof) ::eof)
;; series
(let [api (fn ([]
(GET "/initial"))
([response]
(GET (next-link response))))]
(series api next-link))
@Ramblurr

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@Ramblurr Ramblurr commented Dec 18, 2017

Found this gist via the jira ticket.. I'm tackling the exact problem of properly paging through a http api.

How does one get the result returned by series?

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