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• Find messages from certain key till certain key while being able to remove stale keys.

  - by Alfred

  My problem Let's say I add messages to some sort of datastructure: 1. "dude" 2. "where" 3. "is" 4. "my" 5. "car" Asking for messages from index[4,5] should return: "my","car". Next let's assume that after a while I would like to purge old messages because they aren't useful anymore and I want to save memory. Let's say at time x messages[1-3] became stale. I assume that it would be most efficient to just do the deletion once every x seconds. Next my datastructure should contain: 4. "my" 5. "car" My solution? I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the old messages from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement(efficiently/thread-safe) this or maybe use a library?

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• C++: Declare static variable in function argument list

  - by MDC

  Is there any way at all in C++ to declare a static variable while passing it to a function? I'm looking to use a macro to expand to the expression passed to the function. The expression needs to declare and initialize a static variable on that particular line (based on the filename and line number using FILE and LINE). int foo(int b) { int c = b + 2; return c; } int main() { int a = 3; a = foo(static int h = 2); //<---- see this! cout << a; return 0; } The problem I'm trying to solve is getting the filename and line number with the FILE and LINE macros provided by the preprocessor, but then creating a lookup table with integer keys leading to the FILE, LINE pairs. For example, the key 89 may map to file foo.cpp, line 20. To get this to work, I'm trying to use local static variables, so that they are initialized only once per line execution. The static variable will be initialized by calling a function that calculates the integer key and adds an entry to the lookup table if it is not there. Right now the program uses a message class to send exception information. I'm writing a macro to wrap this class into a new class: WRAPPER_MACRO(old_class_object) will expand to NewClass(old_class_object, key_value). If I add the static variable declaration as a second line right before this, it should work. The problem is that in most places in the code, the old class object is passed as an argument to a function. So the problem becomes declaring and initializing the static variable somehow with the macro, while keeping the existing function calls.

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• crash when using stl vector at instead of operator[]

  - by Jamie Cook

  I have a method as follows (from a class than implements TBB task interface - not currently multithreading though) My problem is that two ways of accessing a vector are causing quite different behaviour - one works and the other causes the entire program to bomb out quite spectacularly (this is a plugin and normally a crash will be caught by the host - but this one takes out the host program as well! As I said quite spectacular) void PtBranchAndBoundIterationOriginRunner::runOrigin(int origin, int time) const // NOTE: const method { BOOST_FOREACH(int accessMode, m_props->GetAccessModes()) { // get a const reference to appropriate vector from member variable // map<int, vector<double>> m_rowTotalsByAccessMode; const vector<double>& rowTotalsForAccessMode = m_rowTotalsByAccessMode.find(accessMode)->second; if (origin != 129) continue; // Additional debug constrain: I know that the vector only has one non-zero element at index 129 m_job->Write("size: " + ToString(rowTotalsForAccessMode.size())); try { // check for early return... i.e. nothing to do for this origin if (!rowTotalsForAccessMode[origin]) continue; // <- this works if (!rowTotalsForAccessMode.at(origin)) continue; // <- this crashes } catch (...) { m_job->Write("Caught an exception"); // but its not an exception } // do some other stuff } } I hate not putting in well defined questions but at the moment my best phrasing is : "WTF?" I'm compiling this with Intel C++ 11.0.074 [IA-32] using Microsoft (R) Visual Studio Version 9.0.21022.8 and my implementation of vector has const_reference operator[](size_type _Pos) const { // subscript nonmutable sequence #if _HAS_ITERATOR_DEBUGGING if (size() <= _Pos) { _DEBUG_ERROR("vector subscript out of range"); _SCL_SECURE_OUT_OF_RANGE; } #endif /* _HAS_ITERATOR_DEBUGGING */ _SCL_SECURE_VALIDATE_RANGE(_Pos < size()); return (*(_Myfirst + _Pos)); } (Iterator debugging is off - I'm pretty sure) and const_reference at(size_type _Pos) const { // subscript nonmutable sequence with checking if (size() <= _Pos) _Xran(); return (*(begin() + _Pos)); } So the only difference I can see is that at calls begin instead of simply using _Myfirst - but how could that possibly be causing such a huge difference in behaviour?

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• Best (functional?) programming language to learn coming from Mathematica

  - by Will Robertson

  As a mechanical engineering PhD student, I haven't had a great pedigree in programming as part of my “day job”. I started out in Matlab (having written some Hypercard and Applescript back in the day, and being introduced to Ada, of all things, in my 1st undergrad year), learned to program—if you can call it that—in (La)TeX; and finally discovered and fell for Mathematica. Now I'm interested in learning a "real" programming language that I can enjoy in the same sort of style as Mathematica, which tries to stress functional programming since it seems to map more nicely to how certain kinds of mathematics can be written algorithmically. So which functional language should I learn? I guess the obvious answer is “as many as possible”, but let's start out humble and give a single, well-considered option a good crack. I've heard good things about, say, Haskell and Scala, but I wonder if (given my non–computer science background) I'd be better off starting in more “grounded” territory and going with Ruby or Python (the latter having the big advantage of being used for Sage, which I'd also like to investigate…after my PhD). Well, I guess this is pretty subjective, so perhaps I could rephrase: would it be better to start looking at Haskell (say) straight after an ad-hoc education to functional programming in Mathematica, or will I get more out of learning Python (say) first? In reference to the question "what do I want to do with it?", I guess my answer is "fun, and learning more". I've got this list of languages that I'd like to look at, and I don't know how to trim them down. And I'd rather start with something a little higher-level than C simply so that I can be somewhat productive without having to re-invent many wheels for any code I'd like to write.

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• How to read pair in freemarker

  - by Lukasz Rys

  Ok i'm having little trouble with reading pair. So I'm creating my pair private Pair<Integer, Integer> count(somethink) { int c1 = 2; int c2 = 4; return new Pair<Integer, Integer>(c1, c2); } And 'sending' it to ftl via java mv.addObject("counted", count(somethink)); I won't write everythink how it sends because I dont think it really matters with my issue. So i'm recieving it in "ftl". Then i was trying to 'read' it <#list counted?keys as key> <a href="#offerOrderTab"><@spring.message "someMsg"/>(${key}/${counted[key]})</a> </#list> After then i'm getting error Expecting a string, date or number here, Expression x is instead a freemarker.ext.beans.SimpleMethodModel As i suppose you dont iterate pairs (or I'm wrong?) i know its pair that contains only one key and one value but still i have to do send it that way and I thought its goin be to similar to iterating through map, in java i would use pair.first() and pair.second() but it doesn't work in ftl (ye i know it shouldnt work). I also tried to cast it to String by using ?string but it didnt work too

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• C# WinForms populating TreeView from List<myObj>

  - by user743354

  I have this structure of classes: public class L3Message { public int Number { get; set; } public string MessageName { get; set; } public string Device { get; set; } public string Time { get; set; } public string ScramblingCode { get; set; } public List<Parameter> Parameters { get; set; } public L3Message() { Parameters = new List<Parameter>(); } } public class Parameter { public int numOfWhitespaces { get; set; } public string ParameterName { get; set; } public string ParameterValue { get; set; } public Parameter Parent { get; set; } public List<Parameter> SubParameters { get; set; } public Parameter() { SubParameters = new List<Parameter>(); } } So, as return type from one of my Methods I have List of L3Messages (List < L3Message ), and I need to map that to TreeView in WinForms (populate TreeView from that List). If possible, I would like to that in separate thread. How can I achieve that?

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• $this->url() to another subdomain

  - by Supertino7

  Hello, I created subdomain for my application. host_www.type = "Zend_Controller_Router_Route_Hostname" host_www.route = "www.mywebsite.com" host_www.defaults.module = "produits" host_www.defaults.controller = "produits" host_www.defaults.action = "index" fiche_boutique.route = "ficheboutique/:boutique" fiche_boutique.defaults.controller = "boutique" fiche_boutique.defaults.action = "fiche-boutique" fiche_boutique.defaults.module = "default" fiche_boutique.chain = "host_www" host_produits.type = "Zend_Controller_Router_Route_Hostname" host_produits.route = "produits.mywebsite.com" host_produits.defaults.module = "produits" host_produits.defaults.controller = "produits" host_produits.defaults.action = "index" fiche_produit.type = "Zend_Controller_Router_Route_Regex" fiche_produit.route = "([-\w]+).htm" fiche_produit.reverse = "%s.htm" fiche_produit.map.1 = "q" fiche_produit.defaults.module = "produits" fiche_produit.defaults.controller = "produits" fiche_produit.defaults.action = "voir-produit" fiche_produit.chain = "host" I don't know if the syntax in this zend config ini file is correct, in particular for routes chaining. Once I'm on this subdomain, urls constructed with $this-url() like this : <a href="<?= $this->url(array('boutique' => 1234), 'fiche_boutique', true) ?>"> Visit this store </a> still point to the subdomain produits.mywebsite.com, where I want it to point to www.mywebsite.com For the moment, I do this : <a href="http://www.mywebsite.com<?= $this->url(array('boutique' => 1234), 'fiche_boutique', true) ?>"> Visit this store </a> But it's not flexible at all. Is there a solution, a parameter to add, or my config file is wrong ? thanks in advance for your help.

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• Fastest reliable way for Clojure (Java) and Ruby apps to communicate

  - by jkndrkn

  Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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• Why does mmap() fail with ENOMEM on a 1TB sparse file?

  - by metadaddy

  I've been working with large sparse files on openSUSE 11.2 x86_64. When I try to mmap() a 1TB sparse file, it fails with ENOMEM. I would have thought that the 64 bit address space would be adequate to map in a terabyte, but it seems not. Experimenting further, a 1GB file works fine, but a 2GB file (and anything bigger) fails. I'm guessing there might be a setting somewhere to tweak, but an extensive search turns up nothing. Here's some sample code that shows the problem - any clues? #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char *argv[]) { char * filename = argv[1]; int fd; off_t size = 1UL << 40; // 30 == 1GB, 40 == 1TB fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666); ftruncate(fd, size); printf("Created %ld byte sparse file\n", size); char * buffer = (char *)mmap(NULL, (size_t)size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if ( buffer == MAP_FAILED ) { perror("mmap"); exit(1); } printf("Done mmap - returned 0x0%lx\n", (unsigned long)buffer); strcpy( buffer, "cafebabe" ); printf("Wrote to start\n"); strcpy( buffer + (size - 9), "deadbeef" ); printf("Wrote to end\n"); if ( munmap(buffer, (size_t)size) < 0 ) { perror("munmap"); exit(1); } close(fd); return 0; }

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• C++ ulong to class method pointer and back

  - by Simone Margaritelli

  Hi guys, I'm using a hash table (source code by Google Inc) to store some method pointers defined as: typedef Object *(Executor::*expression_delegate_t)( vframe_t *, Node * ); Where obviously "Executor" is the class. The function prototype to insert some value to the hash table is: hash_item_t *ht_insert( hash_table_t *ht, ulong key, ulong data ); So basically i'm doing the insert double casting the method pointer: ht_insert( table, ASSIGN, reinterpret_cast<ulong>( (void *)&Executor::onAssign ) ); Where table is defined as a 'hash_table_t *' inside the declaration of the Executor class, ASSIGN is an unsigned long value, and 'onAssign' is the method I have to map. Now, Executor::onAssign is stored as an unsigned long value, its address in memory I think, and I need to cast back the ulong to a method pointer. But this code: hash_item_t* item = ht_find( table, ASSIGN ); expression_delegate_t delegate = reinterpret_cast < expression_delegate_t > (item->data); Gives me the following compilation error : src/executor.cpp:45: error: invalid cast from type ‘ulong’ to type ‘Object* (Executor::*)(vframe_t*, Node*)’ I'm using GCC v4.4.3 on a x86 GNU/Linux machine. Any hints?

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• Mixing stored procedures and ORM

  - by Jason

  The company I work for develops a large application which is almost entirely based on stored procedures. We use classic ASP and SQL Server and the major part of the business logic is contained inside those stored procedures. For example, (I know, this is bad...) a single stored procedure can be used for different purposes (insert, update, delete, make some calculations, ...). Most of the time, a stored procedure is used for operations on related tables, but this is not always the case. We are planning to move to ASP.NET in a near future. I have read a lot of posts on StackOverflow recommending that I move the business logic outside the database. The thing is, I have tried to convince the people who takes the decisions at our company and there is nothing I can do to change their mind. Since I want to be able to use the advantages of object-oriented programming, I want to map the tables to actual classes. So far, my solution is to use an ORM (Entity Framework 4 or nHibernate) to avoid mapping the objects manually (mostly to retrieve the data) and use some kind of Data Access Layer to call the existing stored procedures (for saving). I want your advice on this. Do you think it is a good solution? Any ideas?

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• Mapping element via joining table with NHibernate

  - by NhibernateIdiot

  This is stuff ive done lots of times before but my mind is just blanking at the moment, i will try and give a simple overview of my current situation. I currently have 3 tables as shown below: Office > id, name Person > id, name Office_Personnel > office_id, person_id I then have a model for Person (id, name) and Office, however the Office model contains personnel information: public class Office { int Id {get;set;} string Name {get;set;} ICollection<Person> Personnel {get;set;} } Mapping person is easy, but now im a bit stumped as to why office wont map properly. I chose to use a set when I was mapping the Personnel as there shouldn't be any duplicates, however it doesn't seem to work as I would expect... <set name="Personnel" table="office_personnel" cascade="all"> <key column="office_id" /> <one-to-many class="Person"/> </set> Now one thing that strikes me as odd is that there is no indication as to what person should be binding to (person_id). It keeps trying to find *office_id* column within the Person table. I'm sure this is just some simple problem and im being an idiot, but any help would be great! On a side note, I was weighing up if I should even bother having a middle man table, as I could directly put an Office_Id column within the Person table, but im not 100% sure if in my real project the Person class could be in multiple Offices further down the line...

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• Ruby & ActiveRecord: referring to integer fields by (uniquely mapped) strings

  - by JP

  While its not my application a simple way to explain my problem is to assume I'm running a URL shortener. Rather than attempt to try and figure out what the next string I should use as the unique section of the URL, I just index all my URLs by integer and map the numbers to strings behind the scenes, essentially just changing the base of the number to, let's say, 62: a-z + A-Z + 0-9. In ActiveRecord I can easily alter the reader for the url_id field so that it returns my base 62 string instead of the number being stored in the database: class Short < ActiveRecord::Base def url_id i = read_attribute(:convo) return '0' if i == 0 s = '' while i > 0 s << CHARS[i.modulo(62)] i /= 62 end s end end but is there a way to tell ActiveRecord to accept Short.find(:first,:conditions=>{:url_id=>'Ab7'}), ie. putting the 'decoding' logic into my Short ActiveRecord class? I guess I could define my own def self.find_by_unique_string(string), but that feels like cheating somehow! Thanks!

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• Storing large numbers of varying size objects on disk

  - by Foredecker

  I need to develop a system for storing large numbers (10's to 100's of thousands) of objects. Each object is email-like - there is a main text body, and several ancillary text fields of limited size. A body will be from a few bytes, to several KB in size. Each item will have a single unique ID (probably a GUID) that identifies it. The store will only be written to when an object is added to it. It will be read often. Deletions will be rare. The data is almost all human readable text so it will be readily compressible. A system that lets me issue the I/Os and mange the memory and caching would be ideal. I'm going to keep the indexes in memory, using it to map indexes to the single (and primary) key for the objects. Once I have the key, then I'll load it from disk, or the cache. The data management system needs to be part of my application - I do not want to depend on OS services. Or separately installed packages. Native (C++) would be best, but a manged (C#) thing would be ok. I believe that a database is an obvious choice, but this needs to be super-fast for look up and loading into memory of an object. I am not experienced with data base tech and I'm concerned that general relational systems will not handle all this variable sized data efficiently. (Note, this has nothing to do with my job - its a personal project.) In your experience, what are the viable alternatives to a traditional relational DB? Or would a DB work well for this?

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• How to have variables with dynamic data types in Java?

  - by Nazgulled

  Hi, I need to have a UserProfile class that it's just that, a user profile. This user profile has some vital user data of course, but it also needs to have lists of messages sent from the user friends. I need to save these messages in LinkedList, ArrayList, HashMap and TreeMap. But only one at a time and not duplicate the message for each data structure. Basically, something like a dynamic variable type where I could pick the data type for the messages. Is this, somehow, possible in Java? Or my best approach is something like this? I mean, have 2 different classes (for the user profile), one where I host the messages as Map<K,V> (and then I use HashMap and TreeMap where appropriately) and another class where I host them as List<E> (and then I use LinkedList and ArrayList where appropriately). And probably use a super class for the UserProfile so I don't have to duplicate variables and methods for fields like data, age, address, etc... Any thoughts?

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• How to secure connection strings in VS?

  - by salvationishere

  I see several others have posted this question, however, none of the solutions I've tried have fixed this yet. I have a 32-bit XP running VS 2008 and I am trying to encrypt my connection string in my web.config file. But I am getting the error: The configuration section '...' was not found. Failed! The command I give it: C:\Program Files\Microsoft Visual Studio 9.0\VCAspnet_regiis.exe -pe "system.we b/AdventureWorksConnectionString2" -app "/Documents and Settings/Admin/My Docume nts/Visual Studio 2008/Projects/AddFileToSQL2" Also, how does -app map virtual directory? In other words the path above is the directory right below c:. Is this the correct path to use? And AddFileToSQL2 is the name of my project, although it is part of the AddFileToSQL solution. I have this folder web shared with all of the permissions. And the relevant part of my web.config file: <add name="AdventureWorksConnectionString2" connectionString="Data Source=SIDEKICK;Initial Catalog=AdventureWorks;Persist Security Info=true; User ID=AdventureWorks;Password=sqlMagic" providerName="System.Data.SqlClient" />

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• how do I create a custom route in rails where I pass the id of an existing Model?

  - by Angela

  I created the following route: map.todo "todo/today", :controller => "todo", :action => "show_date" Originally, the 'show_date' action and associated view would display all the activities associated for that day for all the Campaigns. This ended up being very slow on the database...it would generate roughly 30 records but was still slow. So, I'm thinking of creating a partial that would first list the campaigns separately. If someone clicked on a link associated with campaign_id = 1, I want it to go to the following route: todo/today/campaign/1 Then I would like to know how to know that the '1' is the campaign_id in the controller and then just do its thing. The reason I want a distinct URL is so that I can cache this list. I have to keep going back to this and it's slow. NOTE: It's possibly the problem actually is that I've written the queries in a slow way and sqlite isn't representative of how it will be in production, in which case this work-around is unnecessary, but right now, I need a way to get back to the whole list quickly.

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• Extended Zend_Db_Table_Row_Abstract does not return values

  - by WesleyE

  Hi, I'm quite new to Zend and the database classes from it. I'm having problems mapping a Zend_Db_Table_Row_Abstract to my rows. The problem is that whenever I try to map it to a class (Job) that extends the Zend_Db_Table_Row_Abstract class, the database data is not receivable anymore. I'm not getting any errors, trying to get data simply returns null. Here is my code so far: Jobs: class Jobs extends Zend_Db_Table_Abstract { protected $_name = 'jobs'; protected $_rowsetClass = "Job"; public function getActiveJobs() { $select = $this->select()->where('jobs.jobDateOpen < UNIX_TIMESTAMP()')->limit(15,0); $rows = $this->fetchAll($select); return $rows; } } Job: class Job extends Zend_Db_Table_Row_Abstract { public function getCompanyName() { //Gets the companyName for this row (Is on another table), just for example } } Controller: $oJobs = new Jobs(); $aActiveJobs = $oJobs->getActiveJobs(); foreach ($aActiveJobs as $value) { var_dump($value->jobTitle); } When I remove the "protected $_rowsetClass = "Job";" line, so that the table row is not mapped to my own class, I get all the jobTitles perfectly. What am I doing wrong here? Thanks in advance, Wesley

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• How to break out from nested doseqs

  - by fizbin

  Hi, I have a question regarding nested doseq loops. In the start function, once I find an answer I set the atom to true, so that the outer loop validation with :while fails. However it seems that it doesn't break it, and the loops keep on going. What's wrong with it? I am also quite confused with the usage of atoms, refs, agents (Why do they have different names for the update functions when then the mechanism is almost the same?) etc. Is it okay to use an atom in this situation as a flag? Obviously I need a a variable like object to store a state. (def pentagonal-list (map (fn [a] (/ (* a (dec (* 3 a))) 2)) (iterate inc 1))) (def found (atom false)) (defn pentagonal? [a] (let [y (/ (inc (Math/sqrt (inc (* 24 a)))) 6) x (mod (* 10 y) 10)] (if (zero? x) true false))) (defn both-pent? [a b] (let [sum (+ b a) diff (- a b)] (if (and (pentagonal? sum) (pentagonal? diff)) true false))) (defn start [] (doseq [x pentagonal-list :while (false? @found)] (doseq [y pentagonal-list :while (<= y x)] (if (both-pent? x y) (do (reset! found true) (println (- x y)))))))

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• Spring Controller redirect to another page

  - by user1386375

  Hey I got the following problem. This is the content of the jspx file: function postSMTH() { $.ajax({ type: "POST", url: document.getElementById("urltxt").value, data: parameters, }); } <input type="hidden" value="${pageContext.request.contextPath}/foo/foo2/foodat" name="urltxt" id="urltxt"/> <div class="foodat"><a href="javascript:postSMTH();"><spring:message code="foo_foo2_foodat_text" text="FOODAT"/></a></div> So if I push the submit button, the postSMTH function is called and the ajax object is paste to the Controller which look like this: @Controller @RequestMapping(value="/foo") public class FooController { .............. @RequestMapping(value="/foo2", method=RequestMethod.POST) public String homePOST(HttpServletRequest request) { ........ } @RequestMapping(value="/foo2", method=RequestMethod.GET) public String homeGET(HttpServletRequest request) { ........ } @RequestMapping(value="/foo2/foodat", method=RequestMethod.POST) public String doTHAT(HttpServletRequest request) { // check authorization Map fooMap = request.getParameterMap(); // do something in the Database, depending on the paramMap return "redirect:/foo/foo1"; } } Everything is working fine regarding the Database, but the Problem is, that the redirect at the end DOESN'T work. It just stays at the page foo2. I'm new to Spring, maybe its a little mistake somewhere. I just cant make it out by myself. Would be nice if someone would have some hint. Thanks

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• Optimize SQL query (Facebook-like application)

  - by fabriciols

  My application is similar to Facebook, and I'm trying to optimize the query that get user records. The user records are that he as src ou dst. The src is in usermuralentry directly, the dst list are in usermuralentry_user. So, a entry can have one src and many dst. I have those tables: mysql> desc usermuralentry ; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | user_src_id | int(11) | NO | MUL | NULL | | | private | tinyint(1) | NO | | NULL | | | content | longtext | NO | | NULL | | | date | datetime | NO | | NULL | | | last_update | datetime | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ 10 rows in set (0.10 sec) mysql> desc usermuralentry_user ; +-------------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------------+---------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | usermuralentry_id | int(11) | NO | MUL | NULL | | | userinfo_id | int(11) | NO | MUL | NULL | | +-------------------+---------+------+-----+---------+----------------+ 3 rows in set (0.00 sec) And the following query to retrieve information from two users. mysql> explain SELECT * FROM usermuralentry AS a , usermuralentry_user AS b WHERE a.user_src_id IN ( 1, 2 ) OR ( a.id = b.usermuralentry_id AND b.userinfo_id IN ( 1, 2 ) ); +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | 1 | SIMPLE | b | ALL | usermuralentry_id,usermuralentry_user_bcd7114e,usermuralentry_user_6b192ca7 | NULL | NULL | NULL | 147188 | | | 1 | SIMPLE | a | ALL | PRIMARY | NULL | NULL | NULL | 1371289 | Range checked for each record (index map: 0x1) | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ 2 rows in set (0.00 sec) but it is taking A LOT of time... Some tips to optimize? Can the table schema be better in my application?

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• Faster or more memory-efficient solution in Python for this Codejam problem.

  - by jeroen.vangoey

  I tried my hand at this Google Codejam Africa problem (the contest is already finished, I just did it to improve my programming skills). The Problem: You are hosting a party with G guests and notice that there is an odd number of guests! When planning the party you deliberately invited only couples and gave each couple a unique number C on their invitation. You would like to single out whoever came alone by asking all of the guests for their invitation numbers. The Input: The first line of input gives the number of cases, N. N test cases follow. For each test case there will be: One line containing the value G the number of guests. One line containing a space-separated list of G integers. Each integer C indicates the invitation code of a guest. Output For each test case, output one line containing "Case #x: " followed by the number C of the guest who is alone. The Limits: 1 = N = 50 0 < C = 2147483647 Small dataset 3 = G < 100 Large dataset 3 = G < 1000 Sample Input: 3 3 1 2147483647 2147483647 5 3 4 7 4 3 5 2 10 2 10 5 Sample Output: Case #1: 1 Case #2: 7 Case #3: 5 This is the solution that I came up with: with open('A-large-practice.in') as f: lines = f.readlines() with open('A-large-practice.out', 'w') as output: N = int(lines[0]) for testcase, i in enumerate(range(1,2*N,2)): G = int(lines[i]) for guest in range(G): codes = map(int, lines[i+1].split(' ')) alone = (c for c in codes if codes.count(c)==1) output.write("Case #%d: %d\n" % (testcase+1, alone.next())) It runs in 12 seconds on my machine with the large input. Now, my question is, can this solution be improved in Python to run in a shorter time or use less memory? The analysis of the problem gives some pointers on how to do this in Java and C++ but I can't translate those solutions back to Python.

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• create CLLocationCoordinate2D from array

  - by shani

  I have a plist with dictionary of array's with coordinates (stored as strings). I want to create a CLLocationCoordinate2D from every array and crate an overlay for the map. I did that - NSString *thePath = [[NSBundle mainBundle] pathForResource:@"Roots" ofType:@"plist"]; NSDictionary *pointsDic = [[NSDictionary alloc] initWithContentsOfFile:thePath]; NSArray *pointsArray = [NSArray arrayWithArray:[pointsDic objectForKey:@"roade1"]]; CLLocationCoordinate2D pointsToUse[256]; for(int i = 0; i < 256; i++) { CGPoint p = CGPointFromString([pointsArray objectAtIndex:i]); pointsToUse[i] = CLLocationCoordinate2DMake(p.x,p.y); NSLog(@"coord %f",pointsToUse [i].longitude); NSLog(@"coord %f",pointsToUse [i].latitude); } MKPolyline *myPolyline = [MKPolyline polylineWithCoordinates:pointsToUse count:256]; [[self mv] addOverlay:myPolyline]; but the app is crashing without any error. (BTW when i remove the addOverLay method the app does not crash). I have 2 questions- What am i doing wrong? I have tried to set the pointsArray count as the argument for the CLLocationCoordinate2D like that - CLLocationCoordinate2D pointsToUse[pointsArray count]; And i am getting an error. How can i set the CLLocationCoordinate2D dynamically ? Thanks for any help. Shani

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• assign characters to key combinations in XP or Visual Studio .Net

  - by cpj

  I'm running Mac OSX on a MacBookPro (UK keyboard). I run windows XP under parallels in a VM. I run Visual Studio .Net 2003 and 2008 in XP in the VM when i need to. I have English United Kingdom and English United states keyboards setup in XP. (they switch sometimes for no apparent reason) There is no hash "#" key on my mac's keyboard. However, in OSX I can get a hash with an alt+3 key combination. But In Windows XP... I can not make a "#" character. I can go to the character map in windows and copy a hash.. switch into OSX and copy a hash.. search in code and copy a hash.. but I can not make a hash in XP using my keyboard without typing U+0023: ... which you can imagine is annoying. coding anything with hash symbols is becoming a choir. Anyone got any advice or key mapping tricks I can use to get hash characters working in XP using my mac UK keyboard?

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• when to use Hibernate vs. Simple ResultSets for small application

  - by luke

  I just started working on upgrading a small component in a distributed java application. The main application is a rather complicated applet/servlet combo running on JBoss and it extensively uses Hibernate for its DataAccess. The component i am working on however is very a very straightforward data importing service. Basically the workflow is Listen for a network event Parse the data packet, extract a set of identifiers Map the identifier set to a primary key in our database Parse the rest of the packet and insert items in a related table using the foreign key found in step 3 Repeat in the previous version of this component it used a hibernate based DAL, that is no longer usable for a variety of reasons (in particular it is EOL), so I am in charge of replacing the Data Access layer for this component. So on the one hand I think i should use Hibernate because that's what the rest of the application does, but on the other i think i should just use regular java.sql.* classes because my requirements are really straightforward and aren't expected to change any time soon. So my question is (and i understand it is subjective) at what point do you think that the added complexity of using an ORM tool (in terms of configuration, dependencies...) is worth it? UPDATE due to the way the DataAccesLayer for the main application was written (weird dependencies) i cannot easily use it, i would have to implement it myself.

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