Re: lazy sequence termination

2013-05-28 Thread Mond Ray 
Quite a few views but no bites ... what have I done wrong in asking this 
question? If you can't help with the problem would you please take a moment 
to help me understand what has put you off? 

Too much code not enough data? 

Problem too complex to grasp with the supplied info? 

Too dull?

Am I asking too much ... in other words I have got this far and I should be 
expected to know the answer (I really feel like I should too by the way!)

Use of the term Clojurians?

Something else?

Thanks

Ray


On Tuesday, 28 May 2013 13:44:57 UTC+2, Mond Ray wrote:

 Hi Clojurians,

 I have a program which generates a lazy sequence to read ATOM feed chunks. 
 That part works OK but now I want to only take a limited number of the 
 chunks based on some predicate. My predicate is currently returning an 
 empty list so I think (hope!) I am missing something simple.

 Here is an excerpt from the feed (yes the feed is in JSON and I have used 
 cheshire to map to Clojure data):

 {:FEED_ID 5650f3ad-b793-42c6-9fef-80ba105f847d, :TITLE Delta Feed, 
 :UPDATED 2013-05-28T11:15:34.860+02:00, :GENERATOR Products, :LINK 
 {:REL Self, :HREF http://some-url}, :PREVIOUS_LINK {:REL 
 prev-archive, :HREF http://another-url}, .

 Here is the sequence generator:

 (defn fetch-atom-chunk
   Returns an ATOM chunk from the feed-url
   [feed-url]
   (:ATOM_FEED (:body (client/get feed-url {:as :json}

 (defn fetch-atom-feed
   Returns a list of ATOM chunks from the feed-url going back to the 
 from-date
   ;  [feed-url from-date] (fetch-atom-feed feed-url from-date ())
   [feed-url]
   (let [chunk (fetch-atom-chunk feed-url)]
 (lazy-seq
   (cons chunk (fetch-atom-feed (:HREF (:PREVIOUS_LINK chunk)))

 Here is the predicate:

 (defn feed-date-to-clj-date
   Patch for ATOM feed date formats like '2013-05-27T14:35:00.982+02:00'
we have to remove the final ':' from the string to enable its 
 conversion
   [feed-date]
   (.parse (java.text.SimpleDateFormat. -MM-dd'T'HH:mm:ss.SSSZ)
 (str/replace feed-date #(.*)(\d\d):(\d\d) $1$2$3)))

 (defn after?
   Returns true if first-date is after second-date
   [first-date second-date]
   ( (.getTime first-date) (.getTime second-date)))

 (defn more-feed-chunks-needed?
   Look at the atom chunk and decide if we have enough
   [from-date atom-chunk]
   (after? from-date (feed-date-to-clj-date (:UPDATED atom-chunk

 And here is how I run it forever:

 (fetch-atom-feed https://producta.blah.com/feed/current;)

 And here is how I run it with a predicate:

 (def date-from (.parse (java.text.SimpleDateFormat. -MM-dd) 
 2013-05-27))
 (take-while #(more-feed-chunks-needed? date-from %) (fetch-atom-feed 
 https://producta.blah.com/feed/current;))

 Maybe this is too detailed for the group (do let me know) but otherwise I 
 would appreciate your advice / tips on what I could try.

 Thanks

 Ray




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Re: lazy sequence termination

2013-05-28 Thread nchurch 
Could you include the code in client/get?  Not sure where that comes
from and it would be helpful to run the code to see what happensno
guarantees though =)

On May 28, 1:05 pm, Mond Ray mondraym...@gmail.com wrote:
 Quite a few views but no bites ... what have I done wrong in asking this
 question? If you can't help with the problem would you please take a moment
 to help me understand what has put you off?

 Too much code not enough data?

 Problem too complex to grasp with the supplied info?

 Too dull?

 Am I asking too much ... in other words I have got this far and I should be
 expected to know the answer (I really feel like I should too by the way!)

 Use of the term Clojurians?

 Something else?

 Thanks

 Ray







 On Tuesday, 28 May 2013 13:44:57 UTC+2, Mond Ray wrote:

  Hi Clojurians,

  I have a program which generates a lazy sequence to read ATOM feed chunks.
  That part works OK but now I want to only take a limited number of the
  chunks based on some predicate. My predicate is currently returning an
  empty list so I think (hope!) I am missing something simple.

  Here is an excerpt from the feed (yes the feed is in JSON and I have used
  cheshire to map to Clojure data):

  {:FEED_ID 5650f3ad-b793-42c6-9fef-80ba105f847d, :TITLE Delta Feed,
  :UPDATED 2013-05-28T11:15:34.860+02:00, :GENERATOR Products, :LINK
  {:REL Self, :HREF http://some-url}, :PREVIOUS_LINK {:REL
  prev-archive, :HREF http://another-url}, .

  Here is the sequence generator:

  (defn fetch-atom-chunk
    Returns an ATOM chunk from the feed-url
    [feed-url]
    (:ATOM_FEED (:body (client/get feed-url {:as :json}

  (defn fetch-atom-feed
    Returns a list of ATOM chunks from the feed-url going back to the
  from-date
    ;  [feed-url from-date] (fetch-atom-feed feed-url from-date ())
    [feed-url]
    (let [chunk (fetch-atom-chunk feed-url)]
      (lazy-seq
        (cons chunk (fetch-atom-feed (:HREF (:PREVIOUS_LINK chunk)))

  Here is the predicate:

  (defn feed-date-to-clj-date
    Patch for ATOM feed date formats like '2013-05-27T14:35:00.982+02:00'
     we have to remove the final ':' from the string to enable its
  conversion
    [feed-date]
    (.parse (java.text.SimpleDateFormat. -MM-dd'T'HH:mm:ss.SSSZ)
      (str/replace feed-date #(.*)(\d\d):(\d\d) $1$2$3)))

  (defn after?
    Returns true if first-date is after second-date
    [first-date second-date]
    ( (.getTime first-date) (.getTime second-date)))

  (defn more-feed-chunks-needed?
    Look at the atom chunk and decide if we have enough
    [from-date atom-chunk]
    (after? from-date (feed-date-to-clj-date (:UPDATED atom-chunk

  And here is how I run it forever:

  (fetch-atom-feed https://producta.blah.com/feed/current;)

  And here is how I run it with a predicate:

  (def date-from (.parse (java.text.SimpleDateFormat. -MM-dd)
  2013-05-27))
  (take-while #(more-feed-chunks-needed? date-from %) (fetch-atom-feed 
 https://producta.blah.com/feed/current;))

  Maybe this is too detailed for the group (do let me know) but otherwise I
  would appreciate your advice / tips on what I could try.

  Thanks

  Ray

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Re: lazy sequence termination

2013-05-28 Thread Mond Ray 
Ah ... client/get is part of the standard httpclient library so it's not my 
code - it fetches from a url. Sorry I should have included the libraries 
that I used.

On Tuesday, May 28, 2013 10:33:52 PM UTC+2, nchurch wrote:

 Could you include the code in client/get?  Not sure where that comes 
 from and it would be helpful to run the code to see what happensno 
 guarantees though =) 

 On May 28, 1:05 pm, Mond Ray mondraym...@gmail.com wrote: 
  Quite a few views but no bites ... what have I done wrong in asking this 
  question? If you can't help with the problem would you please take a 
 moment 
  to help me understand what has put you off? 
  
  Too much code not enough data? 
  
  Problem too complex to grasp with the supplied info? 
  
  Too dull? 
  
  Am I asking too much ... in other words I have got this far and I should 
 be 
  expected to know the answer (I really feel like I should too by the 
 way!) 
  
  Use of the term Clojurians? 
  
  Something else? 
  
  Thanks 
  
  Ray 
  
  
  
  
  
  
  
  On Tuesday, 28 May 2013 13:44:57 UTC+2, Mond Ray wrote: 
  
   Hi Clojurians, 
  
   I have a program which generates a lazy sequence to read ATOM feed 
 chunks. 
   That part works OK but now I want to only take a limited number of the 
   chunks based on some predicate. My predicate is currently returning an 
   empty list so I think (hope!) I am missing something simple. 
  
   Here is an excerpt from the feed (yes the feed is in JSON and I have 
 used 
   cheshire to map to Clojure data): 
  
   {:FEED_ID 5650f3ad-b793-42c6-9fef-80ba105f847d, :TITLE Delta Feed, 
   :UPDATED 2013-05-28T11:15:34.860+02:00, :GENERATOR Products, :LINK 
   {:REL Self, :HREF http://some-url}, :PREVIOUS_LINK {:REL 
   prev-archive, :HREF http://another-url}, . 
  
   Here is the sequence generator: 
  
   (defn fetch-atom-chunk 
 Returns an ATOM chunk from the feed-url 
 [feed-url] 
 (:ATOM_FEED (:body (client/get feed-url {:as :json} 
  
   (defn fetch-atom-feed 
 Returns a list of ATOM chunks from the feed-url going back to the 
   from-date 
 ;  [feed-url from-date] (fetch-atom-feed feed-url from-date ()) 
 [feed-url] 
 (let [chunk (fetch-atom-chunk feed-url)] 
   (lazy-seq 
 (cons chunk (fetch-atom-feed (:HREF (:PREVIOUS_LINK chunk))) 
  
   Here is the predicate: 
  
   (defn feed-date-to-clj-date 
 Patch for ATOM feed date formats like 
 '2013-05-27T14:35:00.982+02:00' 
  we have to remove the final ':' from the string to enable its 
   conversion 
 [feed-date] 
 (.parse (java.text.SimpleDateFormat. -MM-dd'T'HH:mm:ss.SSSZ) 
   (str/replace feed-date #(.*)(\d\d):(\d\d) $1$2$3))) 
  
   (defn after? 
 Returns true if first-date is after second-date 
 [first-date second-date] 
 ( (.getTime first-date) (.getTime second-date))) 
  
   (defn more-feed-chunks-needed? 
 Look at the atom chunk and decide if we have enough 
 [from-date atom-chunk] 
 (after? from-date (feed-date-to-clj-date (:UPDATED atom-chunk 
  
   And here is how I run it forever: 
  
   (fetch-atom-feed https://producta.blah.com/feed/current;) 
  
   And here is how I run it with a predicate: 
  
   (def date-from (.parse (java.text.SimpleDateFormat. -MM-dd) 
   2013-05-27)) 
   (take-while #(more-feed-chunks-needed? date-from %) (fetch-atom-feed  
  https://producta.blah.com/feed/current;)) 
  
   Maybe this is too detailed for the group (do let me know) but 
 otherwise I 
   would appreciate your advice / tips on what I could try. 
  
   Thanks 
  
   Ray 


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Re: lazy sequence termination

2013-05-28 Thread Michael Gardner 
On May 28, 2013, at 15:05 , Mond Ray mondraym...@gmail.com wrote:

 Quite a few views but no bites ... what have I done wrong in asking this 
 question? If you can't help with the problem would you please take a moment 
 to help me understand what has put you off? 

It would help to post less code, to make it easier for people to zero in on the 
critical parts. For example, it's not necessary to include 'fetch-atom-chunk 
and 'fetch-atom-feed since you can just post some sample parsed data (which you 
did).

When I try running your predicate against your sample data, the predicate 
returns false because 2013-05-27 isn't after the feed's :UPDATED date. Might 
you have the arguments to 'after? reversed?

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Re: lazy sequence termination

2013-05-28 Thread Mond Ray 
Thanks - I wasn't sure how much to assume so that's appreciated. I will 
definitely check for the correctness of the predicate vs the date - that 
would really be a face palm!

OTOH I feel good that I'm actually writing sane Clojure code even if it is 
broken with my data ;-)

Ray

On Tuesday, 28 May 2013 23:46:34 UTC+2, Michael Gardner wrote:

 On May 28, 2013, at 15:05 , Mond Ray mondr...@gmail.com javascript: 
 wrote: 

  Quite a few views but no bites ... what have I done wrong in asking this 
 question? If you can't help with the problem would you please take a moment 
 to help me understand what has put you off? 

 It would help to post less code, to make it easier for people to zero in 
 on the critical parts. For example, it's not necessary to include 
 'fetch-atom-chunk and 'fetch-atom-feed since you can just post some sample 
 parsed data (which you did). 

 When I try running your predicate against your sample data, the predicate 
 returns false because 2013-05-27 isn't after the feed's :UPDATED date. 
 Might you have the arguments to 'after? reversed?

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