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• WeakHashMap iteration and garbage collection

  - by Shamik

  I am using a WeaekHashMap to implement a Cache. I am wondering if I am iterating over the keys of this map, and at the same time garbage collector is actively removing keys from this map, would I receive a ConcurrentModificationException ? I do not think so, because as far as I understand, concurrentmodificationexception happens because of bugs in the application code where the developer forgot to understand that the same map is shared/used by other threads and in this case, it should not happen. But wondering how would JVM handle this when WeakHashMap is not synchronized ?

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• Javascript Pointers question with Dates

  - by Mega Matt

  I noticed this situation in my code (unfortunately), and was able to duplicate it in my own JS file. So I have this code: var date1 = new Date(); // today var date2 = date1; date2 = date2.setDate(date2.getDate() + 1); // what is date1? After this code executes, date1 is today's date + 1! This harkens back to my undergrad days when I learned about pointers, and I guess I'm a little rusty. Is that what's happening here? Obviously I've moved the assignment away from date1, and am only modifying date2, but date1 is being changed. Why is this the case? Incidentally, after this code executes date2 is a long number like 1272123603911. I assume this is the number of seconds in the date, but shouldn't date2 still be a Date object? setDate() should return a Date object... Thanks for the help.

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• Problem with nhibernate join

  - by MexicanHacker

  I'm trying to do a join like this using fluent nhibernate: Id(x => x.Id); Map(x => x.SourceSystemRecordId,"sourceSystemRecord_id"); Then Join("cat.tbl_SourceSystemRecords", SourceSystemRecords); But, it seems I don't have a way to specify the column I want to join with from the first table, in this case I need to join on SourceSystemRecordId and not on Id Is there any way I can specify this? I tried References() but that requires me to create an object for this relationship, what I need is to aggregate the columns in sourcesystem records to the ones in the main table.

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• Should Perl's opendir always return . and .. first?

  - by ojblass

  opendir MYDIR, "$dir"; my @FILES = readdir MYDIR; closedir MYDIR; It appears that 99.9 % of the time the first two entries in the array are always “.” and “..”. Later logic in the script has issues if it is not true. I ran into a case where the directory entries appeared later. Is this indicative of the file system being corrupt or something else? Is there a known order to what opendir returns?

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• Knowledge mining using Hadoop.

  - by Anurag

  Hello there, I want to do a project Hadoop and map reduce and present it as my graduation project. To this, I've given some thought,searched over the internet and came up with the idea of implementing some basic knowledge mining algorithms say on a social websites like Facebook or may stckoverflow, Quora etc and draw some statistical graphs, comparisons frequency distributions and other sort of important values.For searching purpose would it be wise to use Apache Solr ? I want know If such thing is feasible using the above mentioned tools, if so how should I build up on this little idea? Where can I learn about knowledge mining algorithms which are easy to implement using java and map reduce techniques? In case this is a wrong idea please suggest what else can otherwise be done on using Hadoop and other related sub-projects? Thank you

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• Simple question about javascript history.go

  - by Camran

  I have a classifieds website. In every classified, there is a back link which simply takes the browser back one step. This is because when users search classifieds, and click on one to view it, they can easily go back with a link also (instead of only the browser back button). Here is the problem, if the classified is entered directly into the adress bar of a browser, or if somebody bookmarked a classified, then this back-link would take them someplace else... Is there any way of making sure that the previous page is a certain page (index.php in my case)? This way I would only display the back link if the previous page was index.php... Thanks

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• Parse and Break: why break cannot be used for getting out of "any" or "some" rule ?

  - by Rebol Tutorial

  Let say I have to parse a hierarchical set of tags <tag> <subtag1 attr1=value1 attr2=value2> <subtag1 attr1=value1 attr2=value2> <subtag1 attr1=value1 attr2=value2> </tag> Why can't I use break inside some or any to get out of a level hierarchy ? This would allow to do that kind of parsing instead of having a headache to do so ? I'm asking this because I read here http://www.codeconscious.com/rebol/parse-tutorial.html it would create an infinite loop This case produces an infinite loop. Because the BREAK is within a sub-rule of the rule that SOME is processing. The BREAK does not affect success/failure status or the input pointer - it just exits a rule early: rule-to-break: [(print "Break") break] == [(print "Break") break] parse "X" [some [rule-to-break] "X"] Break *Break* ... Break *Break*(escape)

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• Problem in removing hardcoded values using temp table...

  - by Shahsra

  Hi All, First of all Wish u all Happy New Year. I have a problem in writing query. While executing my query I am getting an error. Query: select case when S.R1 = '6' then 5 when S.R1 = '7' then 6 when S.R1 = '8' then 7 when S.R1 = '9' then 8 when S.R1 ='10' then 9 else S.R1 end as Q FROM [HelpService].[dbo].[help] s ----------------------------------------------- SELECT [Source], [Score] INTO #Temp_Q FROM [HelpDesk].[dbo].[Survey] WHERE [data_Source Name] = 'Text Data' ----------------------------------------------- select CONVERT(REAL, a.[Dell Score]) as Q FROM [HelpService].[dbo].[help] s LEFT OUTER JOIN #CE_Temp_Q a on s.[R1] = a.[Source] ERROR Msg 8114, Level 16, State 5, Line 1 Error converting data type varchar to real. What I am asked to do is I need to remove the hard coded values and need to write queries with a temp table. Thanks in Advance, Shashra

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• hunting maven dependencies

  - by Tom

  I want to start using maven in code I distribute but I can't find an efficient way to work with dependencies. Every new dependency takes me far too long to add. As a simple example, I need to add Tomcat for compilation. Do I really have to manually trawl the repo in my browser to find the group-id, artifact-id and version number? In every case it seems easier to find the non-maven downloads. I hope I've missed something obvious.

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• One-to-many relationship related to many tables

  - by Andrey

  I have a scenario where: there are two (or more) tables that represent independent items. lets say Users and Companies Both of these tables need addresses stored. Each one can have one or more address In a normal 1 to many scenario Addresses table woudl just have a UserId or a CompanyId creating a normal 1 to many relationship. In this case i have a few approaches i can think of the Addresses table could have both a UserId and a CompanyId and only one would be used for each record. 2 keys could be used ObjectId and ObjectType So Object id would have a UserId or a CompanyId, and ObjectType woudl be User or Company Create an ObjectTable and add ObjectId to Users and Companies. Addresses would then have an OjbectId I do not really like any of these solutions. i am wondering what is the best approach here. On another note i will most likely user linqtosql for my data access layer.

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• autocomplete-like feature with a python dict

  - by tipu

  In PHP, I had this line matches = preg_grep('/^for/', array_keys($hash)); What it would do is it would grab the words: fork, form etc. that are in $hash. In Python, I have a dict with 400,000 words. It's keys are words I'd like to present in an auto-complete like feature (the values in this case are meaningless). How would I be able to return the keys from my dictionary that match the input? For example (as used earlier), if I have my_dic = t{"fork" : True, "form" : True, "fold" : True, "fame" : True} and I get some input "for", It'll return a list of "fork", "form", "fold"

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• Multiple HTTP request - Rails

  - by bradleyg

  My application checks a number of domains to see if they are valid (approx 100). I have the following code to check a single domain: def self.test_url uri, limit = 10 if limit == 0 return get_error_messages("001") end begin url = URI.parse(uri) response = Net::HTTP.start(url.host, url.port).request_head('/') rescue SocketError => e return get_error_messages("002") end case response when Net::HTTPRedirection then test_url(response['location'], limit - 1) else return get_error_messages(response.code) end end The code checks for the response code while taking into account redirects. This works fine. The only problem I have is when I put this in a loop I want it to run in parallel. So I don't have to wait for domain 1 to respond before I can request domain 2. I have managed this in PHP using curl_multi to run the requests in parallel. Is there a similar thing I can do in Rails?

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• MYSQL - SQL query Getting single record for the similar records and populating other columns with which has more length

  - by Bujji

  Here is my case , I have a database table with below fields name place_code email phone address details estd others and example data if you look at the above example table First three records are talking about XYZ and place code 1020 . I want create a single record for these three records based on substring(name,1,4) place_code ( I am lucky here for all the similar records satisfies this condition and unique in the table .) For the other columns which record column length has max . For example again for the above 3 records email should be [email protected] , phone should be 657890 and details should be "testdetails" This should be done for all the table . (Some has single records and some has max 10 records ) Any help on query that helps me to get the desired result ? Thank You Regards Kiran

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• Finding a integer number after a beginning t=

  - by user2966696

  I have a string like this: 33 00 4b 46 ff ff 03 10 30 t=25562 I am only interested in the five digits at the very end after the t= How can I get this numbers with a regular expression out of it? I tried grep t=..... but I also got all characters including the t= in the beginning, which I would like to drop? After finding that five digit number, I would like to divide this by 1000. So in the above mentioned case the number 25.562. Is this possible with grep and regular expressions? Thanks for your help.

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• cache_counter for habtm

  - by piemesons

  Hello How can use cache_counter in a habtm. For example a question has many tags and a tag can belong to many questions. question habtm tags Now i want to find out number of questions belonging to every tag. One way is counting everytime. But, in case of one_to_many i done same thing in this way. Like one question has many answers. then in answer model i specified belongs_to :question,:cache_counter=>true It solved my problem. So how to do the same in habtm.

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• How can I use Tier Pricing with Configurable Products? (Magento 1.4+)

  - by Rad The Mad

  How can I use/setup Tier Pricing with Configurable Products? (Magento 1.4+) There was an extension to do this but I think it is only for Magento 1.3. Tried to setup tiers in my Simple Products, but those do not show up, or do not activate when I add to cart from my Config Product page. Any help is appreciated! Thanks. Edit: In my case, I would like to use the Tier Pricing FROM the Simple Product. and not use the Tier Pricing from the Config. Product

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• Put Raphael (SVG) canvas behind other divisions to make them clickable?

  - by Kerry

  I am using Raphael to create lines between divisions in an organization chart (or flow chart), but I need to be able to actually click on the divisions and content behind it. If I could make the canvas be behind the other elements, kind of like a background image, that would be idea. Is this possible? UPDATE: I found a solution. Raphael makes an SVG canvas that is absolutely positioned in my case. Absolute positions act as layers, and so to be on top of that layer, my content had to be absolutely positioned as well. If someone else has a better solution, I would be happy to hear it, though this is working fine.

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• Can't use MySQL extract() function in the WHERE clause.

  - by UkraineTrain

  I've run the following query: UPDATE main_table, reference_table SET main_table.calc_column = (CASE WHEN main_table.incr = "6AM" THEN reference_table.col1+reference_table.col2+... WHEN main_table.incr = "12AM" THEN reference_table.col7+reference_table.col8+... WHEN main_table.incr = "6PM" THEN reference_table.col13+reference_table.col14+... ELSE reference_table.col19+reference_table.col20+...) WHERE main_table.month = extract(month from reference_table.thedate) AND main_table.day = extract(day from reference_table.thedate) I've used extract() function since my reference_table doesn't have month and day columns but has the date column named thedate. I've used the extract() function on the reference_table many times before successfully, so, I know that there's nothing wrong with my extract function syntax. However, in this instance, MySQL complains. It probably has to do with the fact that I've used in the WHERE clause. I know that this issue could get fixed if I added the month and day columns to the reference_table to avoid using the extract() function. However, I'm very reluctant to do that and would like to avoid it. How can I make it work?`

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• Why is 'using namespace std;' considered a bad practice in C++?

  - by Mana

  Okay, sorry for the simplistic question, but this has been bugging me ever since I finished high school C++ last year. I've been told by others on numerous occasions that my teacher was wrong in saying that we should have "using namespace std;" in our programs, and that std::cout and std::cin are more proper. However, they would always be vague as to why this is a bad practice. So, I'm asking now: Why is "using namespace std;" considered bad? Is it really that inefficient, or risk declaring ambiguous vars(variables that share the same name as a function in std namespace) that much? Or does this impact program performance noticeably as you get into writing larger applications? I'm sorry if this is something I should have googled to solve; I figured it would be nice to have this question on here regardless in case anyone else was wondering.

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• Multithreading - are the multi-core processors really doing parallel processing?

  - by so.very.tired

  Are the modern multi-core processors really doing parallel processing? Like, take for example, Intel's core i7 processors. some of them has #of Cores: 4 and #of Threads: 8 (taken from Intel's specifications pages). If I to write a program (say in Java or C) that has multiple threads of execution, will they really be processed concurrently? My instructor said that "it is not always the case with multi-core processors", but didn't gave to much details. And why do Intel have to specify both #of Cores and #of Threads? Isn't thread just a term that describe a program-related abstraction, unlike "cores" which are actual hardware? ("Every thread runs on different core").

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• Java generic Interface performance

  - by halfwarp

  Simple question, but tricky answer I guess. Does using Generic Interfaces hurts performance? Example: public interface Stuff<T> { void hello(T var); } vs public interface Stuff { void hello(Integer var); <---- Integer used just as an example } My first thought is that it doesn't. Generics are just part of the language and the compiler will optimize it as though there were no generics (at least in this particular case of generic interfaces). Is this correct?

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• Why I cant be able to change the UITableViewCell detailTextLabel's frame (just the label's position)?

  - by Simon

  Hi.. I am having a table view with default UITableViewCell of style UITableViewCellStyleValue2. I just want to move detailTextLabel few pixels to the right. I know it makes no sense to adjust its width and height :). I am trying to set detailTextLabel's frame with my x and y value. But its not affecting the its frame. I prefer to use default UITableViewCell, in this case, over a customized cell because the default UITableViewCell automatically manages the text alignment and centering of the labels.. How to change UITableViewCell detailTextLabel's frame? Am I allowed to change its frame? Thanks everyone..

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• retrieving data from memcache

  - by Adnan

  Hello, I am starting to learn the benefits of memcache, and would like to implement it on my project. I have understood most of it, such as how data can be retrieved by a key and so on. Now I get it that I can put a post with all of its details in memcache and call the key POST:123, that is OK, and I can do it for each post. But how to deal with the case when I query the table posts to get the list of all posts with their titles. Can this be done with memcache, or should this always be queried from the table?

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• Functioning of Intent.action_pick_activity??

  - by chris

  Hello everybody!! Here is I would like to set up in my application, the function of sharing (facebook, twitter, e-mail) as that of YouTube for example but I get lost little. By looking I saw that apparently it would be necessary to use Intent.action_pick_activity but I do not manage to see how using it on my case. What is that somebody has already implemented this kind of thing? Either what is what somebody knows where I can find examples?? Thanks to all!

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• c++: truth assignment warning with arguments?

  - by John

  I use the following to work with arguments in my programs, but it seems to just hand me a warning (just a warning): "warning: suggest parentheses around assignment used as truth value" The beginning of the code is as follows: enum{OPT_DISP_H = 0x2, OPT_DISP_W = 0x1}; int main(int argc, char *argv[]) { int opt = 0x00; char c; while((++argv)[0] && argv[0][0]=='-'){ while(c =* ++argv[0]) switch(c){ case 'h': opt |= OPT_DISP_H; break; //etc.. The while(c =* ++argv[0]) part being where the warning persists. The code works fine, but what does this warning mean opposed to what is used? I think the code is c = *++argv[0], using the pointer. So why does the single = work and what is really recommended to be used?

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