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  • Return enum instead of bool from function for clarity ?

    - by Moe Sisko
    This is similar to : http://stackoverflow.com/questions/2908876/net-bool-vs-enum-as-a-method-parameter but concerns returning a bool from a function in some situations. e.g. Function which returns bool : public bool Poll() { bool isFinished = false; // do something, then determine if finished or not. return isFinished; } Used like this : while (!Poll()) { // do stuff during wait. } Its not obvious from the calling context what the bool returned from Poll() means. It might be clearer in some ways if the "Poll" function was renamed "IsFinished()", but the method does a bit of work, and (IMO) would not really reflect what the function actually does. Names like "IsFinished" also seem more appropriate for properties. Another option might be to rename it to something like : "PollAndReturnIsFinished" but this doesn't feel right either. So an option might be to return an enum. e.g : public enum Status { Running, Finished } public Status Poll() { Status status = Status.Running; // do something, then determine if finished or not. return status; } Called like this : while (Poll() == Status.Running) { // do stuff during wait. } But this feels like overkill. Any ideas ?

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  • Ant fileset's "dir" missing from absolute path when using a mapper

    - by spaaarky21
    I've been trying to write an Ant task to "compile" Sass scripts in my project using the apply task but I kept getting a "No such file or directory" error. I thought it might have been caused by spaces in the buildpath so I went through the trouble of moving the project only to find that Ant seems to omitting the fileset's root directory when it returns the path. This is what the target looks like: <target name="sass-compile" depends="properties"> <apply executable="sass"> <srcfile /> <targetfile /> <fileset dir="${project.src.dir}" includes="**/*.scss" /> <globmapper from="*.scss" to="*.css" /> </apply> </target> To help troubleshoot, I switched the executable from sass to echo and I noticed that the mapper is transforming paths like this... /Users/me/Documents/Programming/workspace/Project/src/java/com/proj/web/page/template/Template.scss ...into this... /Users/me/Documents/Programming/workspace/Project/java/com/proj/web/page/template/Template.css Notice that the src directory is missing from the target file path. Am I seeing a bug here or is this somehow expected? I would love to know what's going on here. I have also tried using a regexpmapper, and a filtermapper with replacestring. The result is the same. I'm running Ant 1.7.1, which comes bundled with Eclipse Helios, which I'm running on a Mac. I also tried Ant 1.8 on both Mac and Linux. Nothing works. Does anyone have any ideas?

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  • Java - SwingWorker - problem

    - by Yatendra Goel
    I am developing a Java Desktop Application. This app executes the same task public class MyTask implements Callable<MyObject> { in multiple thread simultaneously. Now, when a user clicks on a "start" button, I have created a SwingWorker myWorker and have executed it. Now, this myWorker creates multiple instances of MyTask and submits them to an ExecutorService. Each MyTask instance has a loop and generates an intermediate result at every iteration. Now, I want to collect these intermediate results from each MyTask instances as soon as they are generated. Then after collecting these intermediate results from every MyTask instance, I want to publish it through SwingWorker.publish(MyObject) so that the progress is shown on the EDT. Q1. How can I implement this? Should I make MyTask subclass of SwingWorker instead of Callable to get intermediate results also, because I think that Callable only returns final result. Q2. If the answer of Q1. is yes, then can you give me a small example to show how can I get those intermediate results and aggregate them and then publish them from main SwingWorker? Q3. If I can't use SwingWorker in this situation, then how can I implement this?

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  • Java: split a List into two sub-Lists?

    - by Chris Conway
    What's the simplest, most standard, and/or most efficient way to split a List into two sub-Lists in Java? It's OK to mutate the original List, so no copying should be necessary. The method signature could be /** Split a list into two sublists. The original list will be modified to * have size i and will contain exactly the same elements at indices 0 * through i-1 as it had originally; the returned list will have size * len-i (where len is the size of the original list before the call) * and will have the same elements at indices 0 through len-(i+1) as * the original list had at indices i through len-1. */ <T> List<T> split(List<T> list, int i); [EDIT] List.subList returns a view on the original list, which becomes invalid if the original is modified. So split can't use subList unless it also dispenses with the original reference (or, as in Marc Novakowski's answer, uses subList but immediately copies the result).

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  • Recursion Problems in Prolog

    - by Humble_Student
    I'm having some difficulties in prolog, I'm trying to write a predicate that will return all paths between two cities, although at the moment it returns the first path it finds on an infinite loop. Not sure where I'm going wrong but I've been trying to figure this out all day and I'm getting nowhere. Any help that could be offered would be appreciated. go:- repeat, f([],0,lon,spa,OP,OD), write(OP), write(OD), fail. city(lon). city(ath). city(spa). city(kol). path(lon,1,ath). path(ath,3,spa). path(spa,2,kol). path(lon,1,kol). joined(X,Y,D):- path(X,D,Y);path(Y,D,X). f(Ci_Vi,Di,De,De,PaO,Di):- append([De],Ci_Vi,PaO), !. f(Cities_Visited,Distance,Start,Destination,Output_Path,Output_Distance):- repeat, city(X), joined(Start,X,D), not_member(X,Cities_Visited), New_Distance is Distance + D, f([Start|Cities_Visited],New_Distance,X,Destination,Output_Path,Output_Distance). not_member(X,List):- member(X,List), !, fail. not_member(X,List). The output I'm expecting here is [spa,ath,lon]4 [spa,kol,lon]3. Once again, any help would be appreciated. Many thanks in advance.

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  • pass object from JS to PHP and back

    - by Radu
    This is something that I don't think can't be done, or can't be done easy. Think of this, You have an button inside a div in HTML, when you click it, you call a php function via AJAX, I would like to send the element that start the click event(or any element as a parameter) to PHP and BACK to JS again, in a way like serialize() in PHP, to be able to restore the element in JS. Let me give you a simple example: PHP: function ajaxCall(element){ return element; } JS: callbackFunction(el){ el.color='red'; } HTML: <div id="id_div"> <input type="button" value="click Me" onClick="ajaxCall(this, callbackFunction);" /> </div> So I thing at 3 methods method 1. I can give each element in the page an ID. so the call to Ajax would look like this: ajaxCall(this.id, callbackFunction); and the callback function would be: document.getElementById(el).color='red'; This method I think is hard, beacause in a big page is hard to keep track of all ID's. method 2. I think that using xPath could be done, If i can get the exact path of an element, and in the callback function evaluate that path to reach the element. This method needs some googling, it is just an ideea. method 3. Modify my AJAX functions, so it retain the element that started the event, and pass it to the callback function as argument when something returns from PHP, so in my AJAX would look like this: eval(callbackFunction(argumentsFromPhp, element)); and the callback function would be: callbackFunction(someArgsFromPhp, el){ el.color='red'; // parse someArgsFromPhp } I think that the third option is my choise to start this experiment. Any of you has a better idea how I can accomplish this ? Thank you.

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  • Can a stateless WCF service benefit from built-in database connection pooling?

    - by vladimir
    I understand that a typical .NET application that accesses a(n SQL Server) database doesn't have to do anything in particular in order to benefit from the connection pooling. Even if an application repeatedly opens and closes database connections, they do get pooled by the framework (assuming that things such as credentials do not change from call to call). My usage scenario seems to be a bit different. When my service gets instantiated, it opens a database connection once, does some work, closes the connection and returns the result. Then it gets torn down by the WCF, and the next incoming call creates a new instance of the service. In other words, my service gets instantiated per client call, as in [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]. The service accesses an SQL Server 2008 database. I'm using .NET framework 3.5 SP1. Does the connection pooling still work in this scenario, or I need to roll my own connection pool in form of a singleton or by some other means (IInstanceContextProvider?). I would rather avoid reinventing the wheel, if possible.

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  • How can I prevent default_environment variables from getting set by Capistrano's sudo action?

    - by Logan Koester
    My deploy.rb sets some environment variables to use the regular user's local Ruby rather than the system-wide one. set :default_environment, { :PATH => '/home/myapp/.rvm/bin:/home/myapp/.rvm/bin:/home/myapp/.rvm/rubies/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global/bin:/home/myapp/bin:/usr/bin:/opt/local/bin:/opt/local/sbin:/usr/local/bin:/usr/local/sbin:/usr/sbin:/sbin:/bin:/usr/games', :RUBY_VERSION => 'ruby-1.9.1-p378', :GEM_HOME => '/home/myapp/.rvm/gems/ruby-1.9.1-p378', :GEM_PATH => '/home/myapp/.rvm/gems/ruby-1.9.1-p378:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global' } Naturally, when a task is using sudo, I would expect the system-wide ruby to be used instead. But it seems the environment variables are being set anyway, which is obviously invalid for the root user and returns an error: executing "sudo -p 'sudo password: ' /etc/init.d/god stop" servers: ["myapp.com"] [myapp.com] executing command command finished failed: "env PATH=/home/myapp/.rvm/bin:/home/myapp/.rvm/bin:/home/myapp/.rvm/rubies/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global/bin:/home/myapp/bin:/usr/bin:/opt/local/bin:/opt/local/sbin:/usr/local/bin:/usr/local/sbin:/usr/sbin:/sbin:/bin:/usr/games RUBY_VERSION=ruby-1.9.1-p378 GEM_HOME=/home/myapp/.rvm/gems/ruby-1.9.1-p378 GEM_PATH=/home/myapp/.rvm/gems/ruby-1.9.1-p378:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global sh -c 'sudo -p '\\''sudo password: '\\'' /etc/init.d/god stop'" on myapp.com It makes no difference whether I use capistrano's sudo "system call" or the regular run "sudo system call". How can I avoid this?

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  • Custom rowsetClass does not return values

    - by Wesley
    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 } } 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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  • Unwanted Shell expansion when assigning the output of a shell command to a variable

    - by Rob Goodwin
    I am exporting a portion of a local prototypte svn repository to import into a different repo. We have a number of svn properties set throughout the repo so I figured I would write a script to list the file elements and their corresponding properties. How hard can that be right. So I write started writing a bash script that would assign the output of the svn proplist -v to a variable so I could check if the specified file had any properties. #!/bin/bash svn proplist -v $1 o=$(svn proplist -v "$1") echo $o now this works fine and echos the output of the svn proplist command. But if the proplist command returns something like svn:ignore : * build it performs a shell expansion on the * and inserts the entire directory listing prior to the build property value. So if the directory had a.txt, b.txt and build files/dirs in it, the output would look like. svn:ignore a.txt b.txt build I figure I need to somehow escape the output or something to keep the expansion from happening, but have yet to find something that works. There are other ways to do this, but I hate when I cannot figure something out. and I have to admin, I think this one beat me ( well given the time I can spend on it )

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  • Trying to write a video file using OpenCV

    - by Ted pottel
    Hi , I’m trying to use OpenCV to write a video file. I have a simple program that loads frames from a video file then accepts to save them At first the cvCreateVideoWrite always return NULL. I got a answer from your group saying it returns separate images and to try to change the file name to test0001.png, this worked. But now the cvWriteFrame function always fails, the code is CString path; path="d:\\mice\\Test_Day26_2.avi"; CvCapture* capture = cvCaptureFromAVI(path); IplImage* img = 0; CvVideoWriter *writer = 0; int isColor = 1; int fps = 25; // or 30 int frameW = 640; // 744 for firewire cameras int frameH = 480; // 480 for firewire cameras writer=cvCreateVideoWriter("d:\\mice\\test0001.png",CV_FOURCC('P','I','M','1'), fps,cvSize(frameW,frameH),isColor); if (writer==0) MessageBox("could not open writter"); int nFrames = 50; for(int i=0;i<nFrames;i++){ if (!cvGrabFrame(capture)) MessageBox("could not grab frame"); img=cvRetrieveFrame(capture); // retrieve the captured frame if (img==0) MessageBox("could not retrive data"); if (!cvWriteFrame(writer,img) ) MessageBox("could not write frame"); } cvReleaseVideoWriter(&writer); Any help would be GREAT - Ted

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  • Help Me With This Access Query

    - by yae
    I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are related with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. "Products" table contains all products (p EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obatin the price of the main product, but not runs. This query not returns any value: SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5)); MORE INFO The table "products" contains all the products to sell that it is in the shop. The table "pieces" is to take a control of the compound products. To know those who are the products children. For example of compound product: computers. This product is composed by other products (motherboard, hard disk, memory, cpu, etc.)

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  • getting boost::gregorian dates from a string

    - by Chris H
    I asked a related question yesterday http://stackoverflow.com/questions/2612343/basic-boost-date-time-input-format-question It worked great for posix_time ptime objects. I'm have trouble adapting it to get Gregorian date objects. try { stringstream ss; ss << dateNode->GetText(); using boost::local_time::local_time_input_facet; //using boost::gregorian; ss.imbue(locale(locale::classic(), new local_time_input_facet("%a, %d %b %Y "))); ss.exceptions(ios::failbit); ss>>dayTime; } catch (...) { cout<<"Failed to get a date..."<<endl; //cout<<e.what()<<endl; throw; } The dateNode-GetText() function returns a pointer to a string of the form Sat, 10 Apr 2010 19:30:00 The problem is I keep getting an exception. So concretely the question is, how do I go from const char * of the given format, to a boost::gregorian::date object? Thanks again.

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  • Android 3.1+ USB as virtual COM port

    - by ZachMc
    I have a third party usb device, that when plugged into a Windows machine, is recognized as a serial device and assigned to the COM 4 port. I can communicate with the device just like I would with a device connected via a serial port. For instance, I can write "abc" serially to the device via the USB connection. I have been searching for a way to do a similar thing in Android. If I try the Usb Host method, and use a UsbManager to open the UsbDevice, I can get one interface, with 2 endpoints. I have tried sending control messages using the method in UsbDeviceConnection, but the method returns -1 for everything (though I don't know what I should use for the parameters of that method). Is there a way to get an OutputStream that I can write to that will send bytes to the USB device? Right now I am looking at recompiling the kernel to include a virtual COM port driver and write some native code to be able to do this. Thanks! Edit: I am using the FTDI serial to USB converter circuit. Is this compatible with Android?

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  • (HARD)Remove accents from a JSON response using the raw content

    - by Pentium10
    This is a follow up of this question: Remove accents from a JSON response. The accepted answer there works for a single item/string of a raw JSON content. But I would like to run a full transformation over the entire raw content of the JSON without parsing each object/array/item. What I've tried is this function removeAccents($jsoncontent) { $obj=json_decode($jsoncontent); // use decode to transform the unicode chars to utf $content=serialize($obj); // serialize into string, so the whole obj structure can be used string as a whole $a = 'ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõöøùúûýýþÿRr'; $b = 'aaaaaaaceeeeiiiidnoooooouuuuybsaaaaaaaceeeeiiiidnoooooouuuyybyRr'; $content=utf8_decode($content); $jsoncontent = strtr($content, $a, $b); // at this point the accents are removed, and everything is good echo $jsoncontent; $obj=unserialize($jsoncontent); // this unserialization is returning false, probably because we messed up with the serialized string return json_encode($obj); } As you see after I decoded JSON content, I serialized the object to have a string of it, than I remove the accents from that string, but this way I have problem building back the object, as the unserialize stuff returns false. How can I fix this?

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  • What MS technology to use for HTTP service returning XML?

    - by Borek
    I need to create a service that: accepts HTTP requests (with query string or HTTP POST parameters) does some processing on the requests (checking if the request is valid, authentication etc.) reads data from a custom store (another HTTP call in our case) returns the result as custom XML (defined with XSD) I'm trying to think of various MS technologies that could help me and how good they would be for this scenario (pretty standard one I guess). The tasks above are relatively separate, this is what comes to mind: HTTP front-end: ASP.NET Web Forms ASP.NET MVC (seems more appropriate here as I won't need server controls, view state etc.) WCF? Don't know much about it or how well it would suit my task. Custom logic on the server: this will probably be a generic C# code in all cases (sometimes "plugged into" or called from MVC controllers or some equivalent place in other technologies) Reading data from internal data stores: As said, this is another HTTP server in our case. Options that come to mind: Just read the data using something like WebClient (Just theoretically) implement a LINQ provider (Just even more theoretically) implement an EF provider Output the data as custom XML: Linq2XML Serialization? Is it flexible enough? Does WCF provide some tools for this? Some "OXM" - Object/XML mapper if there is something like that for .NET I may be wrong in many of my assumptions, this is just a quick list that comes to mind after a quick research. Some general notes / questions: Testing is important Solution with a clear domain model would be much preferred over the one without Can Entity Framework actually help somewhere in my scenario? If so, where and how? Would WCF be an appropriate technology for this? I don't know much about it.

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  • How to use sessions in PDO?

    - by Byakugan
    I am still redoing and getting rid of old mysql_* commands in my code. I tried to transfer my session login form old code and this is what I got so far: public function login($user, $password) { if (!empty($user) && !empty($password)) { $password = $web->doHash($user, $password); // in this function is (return sha1(strtoupper($user).':'.strtoupper($password)) $stmt = $db_login->prepare("SELECT * FROM account WHERE username=:user AND pass_hash=:password"); $stmt->bindValue(':user', $user, PDO::PARAM_STR); $stmt->bindValue(':password', $password, PDO::PARAM_STR); $stmt->execute(); $rows = $stmt->rowCount(); if ($rows > 0) { $results_login = $stmt->fetch(PDO::FETCH_ASSOC); $_SESSION['user_name'] = $results_login['username']; $_SESSION['user_id'] = $results_login['id']; return true; } else { return false; } } else { return false; } } After that I am using checks if user logged on site: public function isLogged() { return (!empty($_SESSION['user_id']) && !empty($_SESSION['user_name'])); } But it seems - this function returns always empty because $_SESSION does not exists in PDO? And of course logout is used in this form on my sites: public function logout() { unset($_SESSION['user_id']); unset($_SESSION['user_name']); } But I think PDO has different way of handling session? I did not find any so what is it can i somehow add $_SESSION in PDO withou changing code much? I am using variables $_SESSION['user_name'] and $_SESSION['user_id'] in all over my web project. Summary: 1) How to use sessions in PDO correctly? 2) What is difference between using $stmt->fetch(PDO::FETCH_ASSOC); and $stmt->fetchAll(); Thank you.

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  • LINQ XML query at c# wp7

    - by Karloss
    I am working at Windows Phone 7 C#, Xaml, XML and LINQ programming. I need to organize search by part of the name at following XML: <Row> <Myday>23</Myday> <Mymonth>12</Mymonth> <Mynames>Alex, Joanna, Jim</Mynames> </Row> <Row> <Myday>24</Myday> <Mymonth>12</Mymonth> <Mynames>John, David</Mynames> </Row> I have following query: var myData = from query in loadedData.Descendants("Row") where query.Element("Mynames").Value.Contains("Jo") select new Kalendars { Myday = (int)query.Element("Myday"), Mymonth = (int)query.Element("Mymonth"), Mynames = (string)query.Element("Mynames") }; listBoxSearch.ItemsSource = myData; Query problem is, that it will return full part of the names like "Alex, Joanna, Jim" and "John, David". How can i get only Joanna and John? Second question is how it is possible to do that user enters ...Value.Contains("jo") and query still returns Joanna and John? Possible solution (needs some corrections) public string Search_names { get { return search_names; } set { string line = this.Mynames; string[] names = line.Split(new[] { ", " }, StringSplitOptions.None); var jos = from name in names where name.Contains("is") select name; // ["Joanna"] // HOW TO BIND search_names? } }

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  • class header+ implementation

    - by igor
    what am I doing wrong here? I keep on getting a compilation error when I try to run this in codelab (turings craft) Instructions: Write the implementation (.cpp file) of the GasTank class of the previous exercise. The full specification of the class is: A data member named amount of type double. A constructor that no parameters. The constructor initializes the data member amount to 0. A function named addGas that accepts a parameter of type double . The value of the amount instance variable is increased by the value of the parameter. A function named useGas that accepts a parameter of type double . The value of the amount data member is decreased by the value of the parameter. A function named getGasLevel that accepts no parameters. getGasLevel returns the value of the amount data member. class GasTank{ double amount; GasTank(); void addGas(double); void useGas(double); double getGasLevel();}; GasTank::GasTank(){ amount=0;} double GasTank::addGas(double a){ amount+=a;} double GasTank::useGas(double a){ amount+=a;} double GasTank::getGasLevel(){ return amount;}

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  • Why this base64 function stop working when increasing max length?

    - by flyout
    I am using this class to encode/decode text to base64. It works fine with MAX_LEN up to 512 but if I increase it to 1024 the decode function returns and empty var. This is the function: char* Base64::encode(char *src) { char* ptr = dst+0; unsigned triad; unsigned int d_len = MAX_LEN; memset(dst,'\0', MAX_LEN); unsigned s_len = strlen(src); for (triad = 0; triad < s_len; triad += 3) { unsigned long int sr = 0; unsigned byte; for (byte = 0; (byte<3)&&(triad+byte<s_len); ++byte) { sr <<= 8; sr |= (*(src+triad+byte) & 0xff); } sr <<= (6-((8*byte)%6))%6; // shift left to next 6bit alignment if (d_len < 4) return NULL; // error - dest too short *(ptr+0) = *(ptr+1) = *(ptr+2) = *(ptr+3) = '='; switch(byte) { case 3: *(ptr+3) = base64[sr&0x3f]; sr >>= 6; case 2: *(ptr+2) = base64[sr&0x3f]; sr >>= 6; case 1: *(ptr+1) = base64[sr&0x3f]; sr >>= 6; *(ptr+0) = base64[sr&0x3f]; } ptr += 4; d_len -= 4; } return dst; } Why could be causing this?

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  • Combining aggregate functions in an (ANSI) SQL statement

    - by morpheous
    I have aggregate functions foo(), foobar(), fredstats(), barneystats() I want to create a domain specific query language (DSQL) above my DB, to facilitate using using a domain language to query the DB. The 'language' comprises of boolean expressions (or more specifically SQL like criteria) which I then 'translate' back into pure (ANSI) SQL and send to the underlying Db. The following lines are examples of what the language statements will look like, and hopefully, it will help further clarify the concept: **Example 1** DQL statement: foobar('yellow') between 1 and 3 and fredstats('weight') > 42 Translation: fetch all rows in an underlying table where computed values for aggregate function foobar() is between 1 and 3 AND computed value for AGG FUNC fredstats() is greater than 42 **Example 2** DQL statement: fredstats('weight') < barneystats('weight') AND foo('fighter') in (9,10,11) AND foobar('green') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 3** DQL statement: foobar('green') / foobar('red') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 4** DQL statement: foobar('green') - foobar('red') >= 42 Translation: Fetch all rows where the specified criteria matches Given the following information: The table upon which the queries above are being executed is called 'tbl' table 'tbl' has the following structure (id int, name varchar(32), weight float) The result set returns only the tbl.id, tbl.name and the names of the aggregate functions as columns in the result set - so for example the foobar() AGG FUNC column will be called foobar in the result set. So for example, the first DQL query will return a result set with the following columns: id, name, foobar, fredstats Given the above, my questions then are: What would be the underlying SQL required for Example1 ? What would be the underlying SQL required for Example3 ? Given an algebraic equation comprising of AGGREGATE functions, Is there a way of generalizing the algorithm needed to generate the required ANSI SQL statement(s)? I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible.

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  • In Ruby, how to implement 20 - point and point - 20 using coerce() ?

    - by Jian Lin
    In Ruby, the operation of point - 20 20 - point are to be implemented. But the following code: class Point attr_accessor :x, :y def initialize(x,y) @x, @y = x, y end def -(q) if (q.is_a? Fixnum) return Point.new(@x - q, @y - q) end Point.new(@x - q.x, @y - q.y) end def -@ Point.new(-@x, -@y) end def *(c) Point.new(@x * c, @y * c) end def coerce(something) [self, something] end end p = Point.new(100,100) q = Point.new(80,80) p (-p) p p - q p q - p p p * 3 p 5 * p p p - 30 p 30 - p Output: #<Point:0x2424e54 @x=-100, @y=-100> #<Point:0x2424dc8 @x=20, @y=20> #<Point:0x2424d3c @x=-20, @y=-20> #<Point:0x2424cc4 @x=300, @y=300> #<Point:0x2424c38 @x=500, @y=500> #<Point:0x2424bc0 @x=70, @y=70> #<Point:0x2424b20 @x=70, @y=70> 30 - p will actually be taken as p - 30 by the coerce function. Can it be made to work? I am actually surprise that the - method won't coerce the argument this way: class Fixnum def -(something) if (/* something is unknown class */) a, b = something.coerce(self) return -(a - b) # because we are doing a - b but we wanted b - a, so it is negated end end end that is, the function returns a negated version of a - b instead of just returning a - b.

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  • Has form post behavior changed in modern browsers? (or How are double clicks handled by the browser)

    - by Alex Czarto
    Background: We are in the process of writing a registration/payment page, and our philosophy was to code all validation and error checking on the server side first, and then add client side validation as a second step (un-obstructive jQuery). We wanted to disable double clicks server side, so we wrote some locking, thread-safe code to handle simultaneous posts/race conditions. When we tried to test this, we realized that we could not cause a simultaneous post or race condition to occur. I thought that (in older browsers anyway) double clicking a submit button worked as follows: User double clicks submit button. Browser sends a post on the first click On the second click, browser cancels/ignores initial post, and initiates a second post (before the first post has returned with a response). Browser waits for second post to return, ignoring initial post response. I thought that from the server side it looked like this: Server gets two simultaneous post requests, executes and responds to them both (unaware that no one is listening to the first response). From our testing (FireFox 3.0, IE 8.0) this is what actually happens: User double clicks submit button Browser sends a post for the first click Browser queues up second click, but waits for the response from the first click. Response returns from first click (response is ignored?). Browser sends a post for the second click. So from a server side: Server receives a single post which it executes and responds to. Then, server receives a second request wich it executes and responds to. My question is, has this always worked this way (and I'm losing my mind)? Or is this a new feature in modern browsers that prevents simultaneous posts to be sent to the server? It seems that for server side double click prevention, we don't have to worry about simultaneous posts or race conditions. Only need to worry about queued up posts. Thanks in advance for any feedback / comments. Alex

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  • SQL Query Returning Duplicate Results

    - by Jesse Bunch
    Hi, I've been working out this query now for a while and I thought I had it where I wanted it, but apparently not. There are two records in the database (orders). The query should return two different rows, but instead returns two rows that have exactly the same values. I think it may be something to do with the GROUP BY or derived tables I'm using but my eyes are tired and not seeing the problem. Can any of you help? Thanks in advance. SELECT orders.billerID, orders.invoiceDate, orders.txnID, orders.bName, orders.bStreet1, orders.bStreet2, orders.bCity, orders.bState, orders.bZip, orders.bCountry, orders.sName, orders.sStreet1, orders.sStreet2, orders.sCity, orders.sState, orders.sZip, orders.sCountry, orders.paymentType, orders.invoiceNotes, orders.pFee, orders.shipping, orders.tax, orders.reasonCode, orders.txnType, orders.customerID, customers.firstName AS firstName, customers.lastName AS lastName, customers.businessName AS businessName, orderStatus.statusName AS orderStatus, IFNULL(orderItems.itemTotal, 0.00) + orders.shipping + orders.tax AS orderTotal, IFNULL(orderItems.itemTotal, 0.00) + orders.shipping + orders.tax - IFNULL(payments.totalPayments, 0.00) AS orderBalance FROM orders LEFT JOIN customers ON orders.customerID = customers.id LEFT JOIN orderStatus ON orders.orderStatus = orderStatus.id LEFT JOIN ( SELECT orderItems.orderID, SUM(orderItems.itemPrice * orderItems.itemQuantity) as itemTotal FROM orderItems GROUP BY orderItems.orderID ) orderItems ON orderItems.orderID = orders.id LEFT JOIN ( SELECT payments.orderID, SUM(payments.amount) as totalPayments FROM payments GROUP BY payments.orderID ) payments ON payments.orderID = orders.id

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  • How can I validate/secure/authenticate a JavaScript-based POST request?

    - by Bungle
    A product I'm helping to develop will basically work like this: A Web publisher creates a new page on their site that includes a <script> from our server. When a visitor reaches that new page, that <script> gathers the text content of the page and sends it to our server via a POST request (cross-domain, using a <form> inside of an <iframe>). Our server processes the text content and returns a response (via JSONP) that includes an HTML fragment listing links to related content around the Web. This response is cached and served to subsequent visitors until we receive another POST request with text content from the same URL, at which point we regenerate a "fresh" response. These POSTs only happen when our cached TTL expires, at which point the server signifies that and prompts the <script> on the page to gather and POST the text content again. The problem is that this system seems inherently insecure. In theory, anyone could spoof the HTTP POST request (including the referer header, so we couldn't just check for that) that sends a page's content to our server. This could include any text content, which we would then use to generate the related content links for that page. The primary difficulty in making this secure is that our JavaScript is publicly visible. We can't use any kind of private key or other cryptic identifier or pattern because that won't be secret. Ideally, we need a method that somehow verifies that a POST request corresponding to a particular Web page is authentic. We can't just scrape the Web page and compare the content with what's been POSTed, since the purpose of having JavaScript submit the content is that it may be behind a login system. Any ideas? I hope I've explained the problem well enough. Thanks in advance for any suggestions.

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