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Today's Topics:
1. Re: Nonsensical behavior with http-conduit, httpLbs
(Christopher Allen)
2. Guards problem (Stijn Muylle)
3. Re: Guards problem (Magnus Therning)
4. Re: Guards problem (Dan Serban)
----------------------------------------------------------------------
Message: 1
Date: Thu, 10 Apr 2014 01:40:07 -0500
From: Christopher Allen <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Nonsensical behavior with
http-conduit, httpLbs
Message-ID:
<CADnndOrRhK3=o4MDvYJG=tcdbapehrfdsd0f08qdvujgvsw...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Yeap, it was elasticsearch.
Had to call
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/indices-refresh.htmlto
force update on indexing of documents.
Sorry to bother everybody ;_;
Thank you so much for your help.
Have a great day :)
--- Chris
On Thu, Apr 10, 2014 at 1:28 AM, Michael Snoyman <[email protected]>wrote:
> http-conduit does not perform any kind of automatic concurrency. httpLbs
> will only return after it has fully read the response body from the server.
> So unless there's a bug somewhere in http-conduit, it seems that the server
> has not fully updated its index by the time it gives back a response.
>
>
> On Thu, Apr 10, 2014 at 9:25 AM, Christopher Allen <[email protected]>wrote:
>
>> the function actually running the requests is:
>>
>> dispatch :: String -> Method -> Maybe L.ByteString
>> -> IO Reply
>> dispatch url method body = do
>> initReq <- parseUrl url
>> let reqBody = RequestBodyLBS $ fromMaybe emptyBody body
>> let req = initReq { method = method
>> , requestBody = reqBody
>> , checkStatus = \_ _ _ -> Nothing}
>> withManager $ httpLbs req
>>
>> rest of the code is here: https://github.com/bitemyapp/bloodhound/
>>
>>
>> On Thu, Apr 10, 2014 at 1:25 AM, Christopher Allen <[email protected]>wrote:
>>
>>> It's a step removed from that, and `seq`'ing insertData isn't fixing it,
>>> only a threadDelay is.
>>>
>>> The operations insertData is performing are:
>>> delete index, create index, add document to index
>>>
>>> the operation queryTweet is performing is:
>>> search index
>>>
>>> The behavior seems to indicate "search index" is happening before "add
>>> document to index" and after "delete index", as the document will not exist
>>> when the query is performed.
>>>
>>> Only adding a threadDelay as reliably worked. Even `seq`'ing insertData
>>> doesn't work.
>>>
>>> Are the requests somehow being performed concurrently?
>>>
>>>
>>>
>>> On Thu, Apr 10, 2014 at 1:15 AM, Michael Snoyman <[email protected]>wrote:
>>>
>>>> I can't say I fully understand your code, but it seems like it's doing
>>>> the following:
>>>>
>>>> 1. Send request to server to delete data.
>>>> 2. Send request to server to add data.
>>>> 3. Request data from server.
>>>>
>>>> You're saying that with a long enough delay between steps 2 and 3, then
>>>> (3) works, otherwise it fails. It sounds to me like there's some kind of a
>>>> race condition. I don't know anything about createExampleIndex, but are you
>>>> certain that it only returns after the data is completely ready for
>>>> querying?
>>>>
>>>>
>>>> On Thu, Apr 10, 2014 at 8:43 AM, Christopher Allen
>>>> <[email protected]>wrote:
>>>>
>>>>> to add to my question adding a delay made it work:
>>>>>
>>>>> main :: IO ()
>>>>> main = do
>>>>> _ <- insertData
>>>>> threadDelay 1000000
>>>>> myTweet <- queryTweet
>>>>> print myTweet
>>>>>
>>>>>
>>>>>
>>>>> On Thu, Apr 10, 2014 at 12:41 AM, Christopher Allen <[email protected]
>>>>> > wrote:
>>>>>
>>>>>> Repro'd on GHC 7.8.1 and 7.6.3
>>>>>>
>>>>>> Original code is: https://github.com/bitemyapp/bloodhound/
>>>>>>
>>>>>> The code only works if I manually (out of band) run insertData (in a
>>>>>> REPL) and then run main with the insertData invocation stripped out. If I
>>>>>> run main with the insertData invocation included, it throws an exception
>>>>>> (head) because the search results are empty.
>>>>>>
>>>>>> The behavior is as if queryTweet was executing after insertData
>>>>>> deleted the index, but before it inserted the new data.
>>>>>>
>>>>>> The following is a stripped down example:
>>>>>>
>>>>>> insertData :: IO ()
>>>>>> insertData = do
>>>>>> let encoded = encode exampleTweet
>>>>>> _ <- deleteExampleIndex
>>>>>> created <- createExampleIndex
>>>>>> docCreated <- indexDocument (Server "http://localhost:9200";)
>>>>>> "twitter" "tweet" exampleTweet "1"
>>>>>> print "test"
>>>>>> return ()
>>>>>> el
>>>>>> queryTweet :: IO (Either String Tweet)
>>>>>> queryTweet = do
>>>>>> let queryFilter = BoolFilter (MustMatch (Term "user" "bitemyapp")
>>>>>> False)
>>>>>> <||> IdentityFilter
>>>>>> let search = Search Nothing (Just queryFilter)
>>>>>> reply <- searchByIndex testServer "twitter" search
>>>>>> let result = eitherDecode (responseBody reply) :: Either String
>>>>>> (SearchResult Tweet)
>>>>>> let myTweet = fmap (hitSource . head . hits . searchHits) result
>>>>>> return myTweet
>>>>>>
>>>>>> main :: IO ()
>>>>>> main = do
>>>>>> _ <- insertData
>>>>>> myTweet <- queryTweet
>>>>>> print myTweet
>>>>>>
>>>>>> further up the call chain, the http call is getting dispatched with
>>>>>> http-conduit's gear, the result returned with the expression:
>>>>>>
>>>>>> withManager $ httpLbs req
>>>>>>
>>>>>> Included this in case it affects the semantics.
>>>>>>
>>>>>> Can anybody help? This has stumped me for a couple hours and I
>>>>>> couldn't get anything clueful on IRC.
>>>>>>
>>>>>> Thanks to any that help.
>>>>>>
>>>>>> --- Chris
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Beginners mailing list
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>>>>> http://www.haskell.org/mailman/listinfo/beginners
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>
>> _______________________________________________
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>
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Message: 2
Date: Thu, 10 Apr 2014 09:48:44 +0200
From: Stijn Muylle <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Guards problem
Message-ID:
<cagvaf9a618cdk+s_zr4vzqdxi2y+vh+hoodrcgz82wgavzx...@mail.gmail.com>
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All,
I ran into a small problem using guards, and I don't really understand what
I'm doing wrong.
I have this code:
----------------------------------
import Data.List.Split
type Cell = Bool
data Board = Board [[Cell]] deriving Show
trueList = True : trueList
createBoard :: Int -> Int -> Board
createBoard x y = Board (chunksOf x (take (x * y) trueList))
getCellAt :: Int -> Int -> Board -> Cell
getCellAt x y (Board b)
| x >= (length b) = False
| y >= (length (b !! 0)) = False
| otherwise = (b !! x) !! y
-----------------------------------
When I try to execute this:
getCellAt (-1) 0 $ createBoard 3 3
I get a negative index exception. However, as -1 is smaller than 3 (length
of the board), I would expect False to be returned.
Am I overlooking something?
Thanks!
Stijn
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Message: 3
Date: Thu, 10 Apr 2014 09:58:17 +0200
From: Magnus Therning <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Guards problem
Message-ID:
<caaexw5vta6e025vaakq4j_ghxkdoakugpm4hzy9oquxcq9w...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
On Thu, Apr 10, 2014 at 9:48 AM, Stijn Muylle <[email protected]> wrote:
>
> All,
>
> I ran into a small problem using guards, and I don't really understand what
> I'm doing wrong.
>
> I have this code:
>
> ----------------------------------
> import Data.List.Split
> type Cell = Bool
> data Board = Board [[Cell]] deriving Show
>
> trueList = True : trueList
>
> createBoard :: Int -> Int -> Board
> createBoard x y = Board (chunksOf x (take (x * y) trueList))
>
> getCellAt :: Int -> Int -> Board -> Cell
> getCellAt x y (Board b)
> | x >= (length b) = False
> | y >= (length (b !! 0)) = False
> | otherwise = (b !! x) !! y
>
> -----------------------------------
>
> When I try to execute this:
>
> getCellAt (-1) 0 $ createBoard 3 3
>
> I get a negative index exception. However, as -1 is smaller than 3 (length
> of the board), I would expect False to be returned.
>
> Am I overlooking something?
I might be looking at it wrong, but won't your code go through
1. -1(x) >= 3(length b) ---> not true, so check next guard
2. 0(y) >= 3(length $ b!! 0) ---> not true, so check next guard
3. True(otherwise) ---> true
/M
------------------------------
Message: 4
Date: Thu, 10 Apr 2014 14:23:00 +0300
From: Dan Serban <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Guards problem
Message-ID:
<CAHaPvSdHLXje+d_f5KbAJL5cDw96Ejhio++ow=xc9mlc_n+...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Side note: it's not very clear what you're trying to accomplish, but
you may be better served by using array semantics. I sketched a quick
and dirty code snippet in a hurry, feel free to clean it up and make
it well-typed:
https://gist.github.com/dserban/10370136
After loading it in GHCi, you can do:
?: getCellAt (1,1)
True
?: getCellAt (-1,1)
False
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