Databases
StackOverflow2013
Postsdbo
POReduce a lazy sequence like a loop with a condition in Clojure
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POReduce a lazy sequence like a loop with a condition in Clojure
    primarykey
    data
    text
    <p>I have an infinite lazy sequence that produce a "preamble" and a "pattern repetition", a simple example of this kind of sequence could be implemented in Clojure with:</p> <pre><code>(def infinite-lazy-sequence (lazy-cat [4] (cycle [1 2 3]))) =&gt; (take 20 infinite-lazy-sequence) (4 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1) </code></pre> <p>I would like to get a <code>set</code> of the elements forming this <code>infinite-lazy-sequence</code>, here is a way to implement it using <code>loop</code>:</p> <pre><code>(loop [[head &amp; tail] infinite-lazy-sequence result #{}] (if (contains? result head) result (recur tail (conj result head)))) =&gt; #{1 2 3 4} </code></pre> <p>Here is the question: is it possible to achieve the same result using <code>reduce</code>? And using <code>take-while</code>?</p> <p><strong>Edit:</strong></p> <p><em>Benchmark results using clojure-1.5.1 and perforate-0.2.4</em></p> <p>proposed <code>loop-recur</code> implementation:</p> <pre><code>Case: :loop-recur Evaluation count : 60 in 60 samples of 1 calls. Execution time mean : 1.054975 sec Execution time std-deviation : 26.316442 ms Execution time lower quantile : 1.026187 sec ( 2.5%) Execution time upper quantile : 1.125854 sec (97.5%) </code></pre> <p>@sw1nn <code>reduce-reduced</code> implementation:</p> <pre><code>Case: :reduce-reduced Evaluation count : 120 in 60 samples of 2 calls. Execution time mean : 875.091831 ms Execution time std-deviation : 19.745142 ms Execution time lower quantile : 850.871606 ms ( 2.5%) Execution time upper quantile : 921.947759 ms (97.5%) </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USFilippo Vitale
    1. USFilippo Vitale
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POReduce a lazy sequence like a loop with a condition in Clojure
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POReduce a lazy sequence like a loop with a condition in Clojure
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POReduce a lazy sequence like a loop with a condition in Clojure
      1. USchrsan
      1. VTFavorite
    1. COSo no element in your infinite sequence may occur twice before the repeated pattern starts repeating, is that correct?
      singulars
      1. POReduce a lazy sequence like a loop with a condition in Clojure
      1. USsvk
    2. COYes, it is correct. Unfortunately I don't know how long the preamble could be... Good point.
      singulars
      1. POReduce a lazy sequence like a loop with a condition in Clojure
      1. USFilippo Vitale
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload