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• Apache Cordova (Phonegap): is jsop needed for cross-site scripting?

  - by DEX

  I've just started using Apache Cordova. I have an library that makes calls (via ajax) to a soap server. When I run these on my local machine in chrome, I get cross site scripting errors when trying to make calls to the service. When I run the same exact code using the Cordova browser in the iOS emulator, the scripts seem to hit the server fine and the response data is received properly. So my question is how is the Cordova browser able to make these requests without cross-site scripting permissions & JSONP ? One thing I noticed is that when the request is sent from iOS, there is no "Origin" header. Is this allowing the Cordova browser to stealthily circumvent cross-site scripting requirements? Is it possible that the node.js server on the device (I believe this is how Cordova works) is manipulating the headers to allow this? I'd like to avoid enabling cross-site scripting on my site so I think this "feature" is nice, but I'm wondering if it's a security hole as well. Anyone have experience with this?

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• How to convert a lambda to an std::function using templates

  - by retep998

  Basically, what I want to be able to do is take a lambda with any number of any type of parameters and convert it to an std::function. I've tried the following and neither method works. std::function([](){});//Complains that std::function is missing template parameters template <typename T> void foo(function<T> f){} foo([](){});//Complains that it cannot find a matching candidate The following code does work however, but it is not what I want because it requires explicitly stating the template parameters which does not work for generic code. std::function<void()>([](){}); I've been mucking around with functions and templates all evening and I just can't figure this out, so any help would be much appreciated. As mentioned in a comment, the reason I'm trying to do this is because I'm trying to implement currying in C++ using variadic templates. Unfortunately, this fails horribly when using lambdas. For example, I can pass a standard function using a function pointer. template <typename R, typename...A> void foo(R (*f)(A...)) {} void bar() {} int main() { foo(bar); } However, I can't figure out how to pass a lambda to such a variadic function. Why I'm interested in converting a generic lambda into an std::function is because I can do the following, but it ends up requiring that I explicitly state the template parameters to std::function which is what I am trying to avoid. template <typename R, typename...A> void foo(std::function<R(A...)>) {} int main() { foo(std::function<void()>([](){})); }

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• Unable to delete inherited entity class in EF4

  - by Coding Gorilla

  I have two entities in an EF4 model (using Model First), let's call them EntityA and EntityB. EntityA is marked as abstract, and EntityB inherits from EntityA. They are similar to the following: public class EntityA { public Guid Id; public string Name; public string Uri; } public class EntityB : EntityA { public string AnotherProperty; } The generated database tables look as I would expect them, with EntityA as on table, and then another table like: EntityA_EntityB Id (PK, FK, uniqueidentifier) AnotherProperty (varchar) There is a foreign key constraint on EntityA_EntityB that references EntityA's Id property, no cascades are configured (although I did try changing these myself). The problem is that when I attempt to do something like: Context.DeleteObject(EntityA_EntityB); EF attempts to delete the EntityA_EntityB table record before deleting the EntityA table record, which of course violates the foreign key constraint on EntityA_EntityB table. Using EFProfiler I see the following commands being sent to the database: delete [dbo].[EntityA_EntityB] where (([Id] = '5c02899f-09ea-2ed9-d44b-01aef80f6b64' /* @0 */) followed by delete [dbo].[EntityA] where ([Id] = '5c02899f-09ea-2ed9-d44b-01aef80f6b64' /* @0 */) I'm completely stumped as to how to get around this problem. I would think the EF should know that it needs to delete the base class first, before deleting the inherited class. I know I could do some triggers or other database type solutions, but I'd rather avoid doing that if I can. All my classes are POCO built using some customized T4 templates. I don't want to paste in a lot of extraneous code, but if you need more information I'll provide what I can.

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• Caching vector addition over changing collections

  - by DRMacIver

  I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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• Tree iterator, can you optimize this any further?

  - by Ron

  As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

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• Why doesn't String's hashCode() cache 0?

  - by polygenelubricants

  I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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• How to retrieve content via .load() or $.get() with this line

  - by Sin

  hello :) I posted a question a day or two ago about how to retrieve php via ajax method in this modal I was using. I kinda found out the right way to go about it, but there's still something I'm not doing right (obviously lol) Here's the section thats giving me the issues: jQuery('div that holds content').fadeIn(200).css({ 'width': Number( popWidth ) }); $('').load('/something/somewhere/this #content'); So, im using safari, and a local server (mamp), when I check activity in my browser, it shows that it is loading the content with every click, AND the pop up pops up, but no content. When I simply retrieve content via hidden div, ofcourse, i get it. This is what I'm trying to avoid. right now I have that div in my footer stashed as hidden. I'd rather just make a call when its needed, instead of loading it every single time a page is accessed. you can go here to see the whole script i posted in my last question: How to use ajax to show php in a modal pop up Anyone have any idea? I read that .load() has the ability to grab specific content from a request, but im not sure the major difference between that and $.get() I've tried both, and I get the same results. Im using wordpress, and wordpress's ajax requests run smooth as ever, so I know its not a local problem, i'ts my coding lol Ok....Im done typing :)

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• Why null reference exception in SetMolePublicInstance?

  - by OldGrantonian

  I get a "null reference" exception in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, null); The program builds and compiles correctly. There are no complaints about any of the parameters to the method. Here's the specification of SetMolePublicInstance, from the object browser: SetMolePublicInstance(System.Delegate _stub, System.Type receiverType, object _receiver, string name, params System.Type[] parameterTypes) Here are the parameter values for "Locals": + stub {Method = {System.String <StaticMethodUnitTestWithDeq>b__0()}} System.Func<string> + receiverType {Name = "OrigValue" FullName = "OrigValueP.OrigValue"} System.Type {System.RuntimeType} objReceiver {OrigValueP.OrigValue} object {OrigValueP.OrigValue} name "TestString" string parameterTypes null object[] I know that TestString() takes no parameters and returns string, so as a starter to try to get things working, I specified "null" for the final parameter to SetMolePublicInstance. As already mentioned, this compiles OK. Here's the stack trace: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.ExtendedReflection.Collections.Indexable.ConvertAllToArray[TInput,TOutput](TInput[] array, Converter`2 converter) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMole(Delegate _stub, Type receiverType, Object _receiver, String name, MoleBindingFlags flags, Type[] parameterTypes) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(Delegate _stub, Type receiverType, Object _receiver, String name, Type[] parameterTypes) at DeqP.Deq.Replace[T](Func`1 stub, Type receiverType, Object objReceiver, String name) in C:\0VisProjects\DecP_04\DecP\DeqC.cs:line 38 at DeqPTest.DecCTest.StaticMethodUnitTestWithDeq() in C:\0VisProjects\DecP_04\DecPTest\DeqCTest.cs:line 28 at Starter.Start.Main(String[] args) in C:\0VisProjects\DecP_04\Starter\Starter.cs:line 14 Press any key to continue . . . To avoid the null parameter, I changed the final "null" to "parameterTypes" as in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, parameterTypes); I then tried each of the following (before the line): int[] parameterTypes = null; // if this is null, I don't think the type will matter int[] parameterTypes = new int[0]; object[] parameterTypes = new object[0]; // this would allow for various parameter types All three attempts produce a red squiggly line under the entire line for SetMolePublicInstance Mouseover showed the following message: The best overloaded method match for 'Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(System.Delegate, System.Type, object, string, params System.Type[])' has some invalid arguments. I'm assuming that the first four arguments are OK, and that the problem is with the params array.

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• are there requirements for Struts setters beyond variable name matching?

  - by slk

  I have a model-driven Struts Web action: public class ModelDrivenAction<T extends Object> implements ModelDriven<T>, Preparable { protected Long id; protected T model; @Override public void prepare() {} public void setId(Long id) { this.id = id; } @Override public T getModel() { return model; } public void setModel(T model) { this.model = model; } } I have another action which is not currently model-driven: public class OtherAction implements Preparable { private ModelObj modelObj; private Long modelId; @Override public void prepare() { modelObj = repoService.retrieveModelById(modelId); } public void setModelId(Long modelId) { this.modelId = modelId; } } I wish to make it so, and would like to avoid having to track down all the instances in JavaScript where the action is passed a "modelId" parameter instead of "id" if at all possible. I thought this might work, so either modelId or id could be passed in: public class OtherAction extends ModelDrivenAction<ModelObj> { @Override public void prepare() { model = repoService.retrieveModelById(id); } public void setModelId(Long modelId) { this.id = modelId; } } However, server/path/to/other!method?modelId=123 is failing to set id. I thought so long as a setter matched a parameter name the Struts interceptor would call it on action invocation. Am I missing something here?

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• A better way of getting a data table with various column types into string array

  - by Vlad

  This should be an easy one, looks like I got myself too confused. I get a table from a database, data ranges from varchar to int to Null values. Cheap and dirty way of converting this into a tab-delimited file that I already have is this (shrunken to preserve space, ugliness is kept on par with original): da.Fill(dt) ' da - DataAdapter ' ' dt - DataTable ' Dim lColumns As Long = dt.Columns.Count Dim arrColumns(dt.Columns.Count) As String Dim arrData(dt.Columns.Count) As Object Dim j As Long = 0 Dim arrData(dt.Columns.Count) As Object For i = 0 To dt.Rows.Count - 1 arrData = dt.Rows(i).ItemArray() For j = 0 To arrData.GetUpperBound(0) - 1 arrColumns(j) = arrData(j).ToString Next wrtOutput.WriteLine(String.Join(strFieldDelimiter, arrColumns)) Array.Clear(arrColumns, 0, arrColumns.GetLength(0)) Array.Clear(arrData, 0, arrData.GetLength(0)) Next Not only this is ugly and inefficient, it is also getting on my nerves. Besides, I want, if possible, to avoid the infamous double-loop through the table. I would really appreciate a clean and safe way of rewriting this piece. I like the approach that is used here - especially that is trying to solve the same problem that I have, but it crashes on me when I apply it to my case directly.

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• How to create a desktop shortcut to a website with website logo as icon?

  - by Wbdvlpr

  Hi I need a solution which allows users to create a desktop shortcut to a website, preferably with website logo as shortcut icon. There are ways users can create shortcut such as drag drop favicon or right click create new shortcut etc. This works but also creates the shortcut with default IE icon on windows. I am trying to avoid this method for this icon and some other reasons. I thought of creating a website-title.URL file, and tell users to download and save file to their desktop, again this works but doesn't solve the icon problem as the website logo (.ico) has to be at local disk and at a pre-specified location [IconFile=path]. I was wondering if it is possible to create a some sort of installer or windows application which users can download from the website. Once its executed by user, it creates this .URL file on user desktop which have IconFile path pre-specified, and copy the website-logo.ico at path specified in .URL file etc. So my questions are - Is it possible to create such a solution? What programming languages can be used to achieve this? Can this installer/app be made to work on non-windows machines as well? From developments point of view how big project it is? if I have to hire a programmer to do this. Please let me know if you need more information. Thanks

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• Could I return a FileStream as a generic interface to a file?

  - by Eric

  I'm writing a class interface that needs to return references to binary files. Typically I would provide a reference to a file as a file path. However, I'm considering storing some of the files (such as a small thumbnail) in a database directly rather then on a file system. In this case I don't want to add the extra step of reading the thumbnail out of the database onto the disc and then returning a path to the file for my program to read. I'd want to stream the image directly out of the database into my program and avoid writing anything to the disc unless the user explicit wants to save something. Would having my interface return a FileStreamor even a Imagemake sense? Then it would be up to the implementing class to determine if the source of the FileStream or Image is a file on a disc or binary data in a database. public interface MyInterface { string Thumbnail {get;} string Attachment {get;} } vs public interface MyInterface { Image Thumbnail {get;} FileStream Attachment {get;} }

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• How do I fix the alpha value after calling GDI text functions?

  - by Daniel Stutzbach

  I have a application that uses the Aero glass effect, so each pixel has an alpha value in addition to red, green, and blue values. I have one custom-draw control that has a solid white background (alpha = 255). I would like to draw solid text on the control using the GDI text functions. However, these functions set the alpha value to an arbitrary value, causing the text to translucently show whatever window is beneath my application's. After calling rendering the text, I would like to go through all of the pixels in the control and set their alpha value back to 255. What's the best way to do that? I haven't had any luck with the BitBlt, GetPixel, and SetPixel functions. They appear to be oblivious to the alpha value. Here are other solutions that I have considered and rejected: Draw to a bitmap, then copy the bitmap to the device: With this approach, the text rendering does not make use of the characteristics of the monitor (e.g., ClearText). Use GDI+ for text rendering: This application originally used GDI+ for text rendering (before I started working on Aero support). I switched to GDI because of difficulties I encountered trying to accurately measure strings with GDI+. I'd rather not switch back. Set the Aero region to avoid the control in question: My application's window is actually a child window of a different application running in a different process. I don't have direct control over the Aero settings on the top-level window. The application is written in C# using Windows Forms, though I'm not above using Interop to call Win32 API functions.

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• Free cross-platform library to convert numbers (money amounts) to words?

  - by bialix

  I'm looking for cross-platform library which I can use in my C application to convert money amounts (e.g. $123.50) to words (one hundred twenty three dollars and fifty cents). I need support for multiple currencies: dollars, euros, UK pounds etc. Although I understand this is not hard at all to write my own implementation, but I'd like to avoid reinventing wheel. I've tried to google it, but there is too much noise related to MS Word converters. Can anybody suggest something? UPDATE numerous comments suggest to write my own implementation because it's really easy task. And I agree. My point was about support of multiple currencies in the same time and different business rules to spell the amounts (should be fractional part written as text or numbers? etc.) As I understand serious business applications have such library inside, but I think there is nothing open-source available, maybe because it seems as very easy task. I'm going to write my own libary and then open-source it. Thanks to all.

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• Send email from webpage without postback/refresh

  - by jb

  Hi all. Long time reader, first time writer. Quick query i hope someone can help me with. I have a webpage (php, javascript) which has a small contact form for a user to fill in and email us. Not a problem in itself, i have a working form already. Nothing noteworthy, just a form posting to a php page which sends an email. <form id="myform" name="myform" method="post" action="Mailer.php"> So user fills in form, hits submit and the page changes to mailer.php and they find their way back to where they were. What I want instead is for the to stay on the same page when submit is pushed. The form div to update itself to just say 'message sent' or something. I just want to avoid a full page refresh. Much like how on say facebook, commenting on a status only updates that div. Hope that is phrased clearly enough. Cheers all,

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• Performance when querying a View

  - by Nate Bross

  I'm wondering if this is a bad practice or if in general this is the correct approach. Lets say that I've created a view that combines a few attributes from a few tables. My question, what do I need to do so I can query against this view as if it were a table without worrying about performance? All attributes in the original tables are indexed, my concern is that the result view will have hundreds of thousands of records, which I will want to narrow down quite a bit based on user input. What I'd like to avoid, is having multiple versions of the code that generates this view floating around with a few extra "where" conditions to facilitate the user input filtering. For example, assume my view has this header VIEW(Name, Type, DateEntered) this may have 100,000+ rows (possibly millions). I'd like to be able to make this view in SQL Server, and then in my application write querlies like this: SELECT Name, Type, DateEntered FROM MyView WHERE DateEntered BETWEEN @date1 and @date2; Basically, I am denormalizing my data for a series of reports that need to be run, and I'd like to centralize where I pull the data from, maybe I'm not looking at this problem from the right angle though, so I'm open to alternative ways to attack this.

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• Modeling Buyers & Sellers in a Rails Ecommerce App

  - by MikeH

  I'm building a Rails app that has Etsy.com style functionality. In other words, it's like a mall. There are many buyers and many sellers. I'm torn about how to model the sellers. Key facts: There won't be many sellers. Perhaps less than 20 sellers in total. There will be many buyers. Hopefully many thousands :) I already have a standard user model in place with account creation and roles. I've created a 'role' of 'seller', which the admin will manually apply to the proper users. Since we'll have very few sellers, this is not an issue. I'm considering two approaches: (1) Create a 'store' model, which will contain all the relevant store information. Products would :belong_to :store, rather than belonging to the seller. The relationship between the user and store models would be: user :has_one store. My main problem with this is that I've always found has_one associations to be a little funky, and I usually try to avoid them. The app is fairly complex, and I'm worried about running into a cascade of problems connected to the has_one association as I get further along into development. (2) Simply include the relevant 'store' information as part of the user model. But in this case, the store-related db columns would only apply to a very small percentage of users since very few users will also be sellers. I'm not sure if this is a valid concern or not. It's very possible that I'm thinking about this incorrectly. I appreciate any thoughts. Thanks.

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• Can it be important to call remove() on an EJB 3 stateless session bean? Perhaps on weblogic?

  - by Michael Borgwardt

  I'm in the process of migrating an EJB 2 application to EJB 3 (and what a satisfying task it is to delete all those deployment descriptors!). It used to run on Weblogic and now runs on Glassfish. The task is going very smoothly, but one thing makes me wary: The current code takes great care to ensure that EJBObject.remove() is called on the bean when it's done its job, and other developers have (unfortunately very vague) memories of "bad things" happening when that was not done. However, with EJB3, the implementation class does not implement EJBObject, so there is no remove() method to be called. And my understanding is that there isn't really any point at all in calling it on stateless session beans, since they are, well, stateless. Could these "bad things" have been weblogic-specific? If not, what else? Should I avoid the full EJB3 lightweightness and keep a remote interface that extends EJBObject? Or just write it off as cargo-cult programming and delete all those try/finally clauses? I'm leaning towards the latter, but now feeling very comfortable with it.

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• Android 2.0+ account duplication

  - by Stoyan

  I know that you can setup accounts in Android 2.0+ and thats great but as i have recently found out, it can create duplication. My phone(Sprint HTC hero 2.1-upadate1) comes with HTC Sense and thats great, it also has Peep pre-installed and it asked me when i setup the phone to add a twitter account, and so i did. I can now open peep and it all works, perfect. But I decided i wanted to try the Twitter for Android app. I installed it and it also asked me to create a twitter account, not good. I did create the new account and the app worked just like it was supposed to. Then when i go into my accounts i can see that i have two twitter accounts(the same one). Is this something that can be avoided in the programming or is this something that can be fixed with the os? I also noticed the same for the facebook account. Is there something in the SDK that can prevent this...or combine the accounts after the fact? or is this all completely up to the developers. If its up to the developers then i would really like to see some code/documentation so i can avoid such things.

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• jQuery - Wait until image loads before performing function

  - by Steven

  I'm trying to create a simple portfolio page. I have a list of thumbs and an image. When you click on a thumb, the image will change. When a thumbnail is clicked, I'd like to have the image fade out, wait until the image is loaded, then fade back in. The problem I have right now is that some of the images are pretty big, so it fades out, then fades back in immediately, sometimes while the image is still loading. I'd like to avoid using setTimeout, since sometimes an image will load faster or slower than the time I set. Here's my code: $(function() { $('img#image').attr("src", $('ul#thumbs li:first img').attr("src")); $('ul#thumbs li img').click(function() { $('img#image').fadeOut(700); var src = $(this).attr("src"); $('img#image').attr("src", src); $('img#image').fadeIn(700); }); }); <img id="image" src="" alt="" /> <ul id="thumbs"> <li><img src="/images/thumb1.png" /></li> <li><img src="/images/thumb2.png" /></li> <li><img src="/images/thumb3.png" /></li> </ul>

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• Consequent attribute calculations with a queuing system

  - by vrinek

  For all of the following assume these: rails v3.0 ruby v1.9 resque We have 3 models: Product belongs_to :sku, belongs_to :category Sku has_many :products, belongs_to :category Category has_many :products, has_many :skus When we update the product (let's say we disable it) we need to have some things happen to the relevant sku and category. The same is true for when a sku is updated. The proper way of achieving this is have an after_save on each model that triggers the other models' update events. example: products.each(&:disable!) # after_save triggers self.sku.products_updated # and self.category.products_updated (self is product) Now if we have 5000 products we are in for a treat. The same category might get updated hundreds of times and hog the database while doing so. We also have a nice queueing system, so the more realisting way of updating products would be products.each(&:queue_disable!) which would simply toss 5000 new tasks to the working queue. The problem of 5000 category updates still exists though. Is there a way to avoid all those updates on the db? How can we concatenate all the category.products_updated for each category in the queue?

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• Using "from __future__ import division" in my program, but it isn't loaded with my program

  - by Sara Fauzia

  I wrote the following program in Python 2 to do Newton's method computations for my math problem set, and while it works perfectly, for reasons unbeknownst to me, when I initially load it in ipython with %run -i NewtonsMethodMultivariate.py, the Python 3 division is not imported. I know this because after I load my Python program, entering x**(3/4) gives "1". After manually importing the new division, then x**(3/4) remains x**(3/4), as expected. Why is this? # coding: utf-8 from __future__ import division from sympy import symbols, Matrix, zeros x, y = symbols('x y') X = Matrix([[x],[y]]) tol = 1e-3 def roots(h,a): def F(s): return h.subs({x: s[0,0], y: s[1,0]}) def D(s): return h.jacobian(X).subs({x: s[0,0], y: s[1,0]}) if F(a) == zeros(2)[:,0]: return a else: while (F(a)).norm() > tol: a = a - ((D(a))**(-1))*F(a) print a.evalf(10) I would use Python 3 to avoid this issue, but my Linux distribution only ships SymPy for Python 2. Thanks to the help anyone can provide. Also, in case anyone was wondering, I haven't yet generalized this script for nxn Jacobians, and only had to deal with 2x2 in my problem set. Additionally, I'm slicing the 2x2 zero matrix instead of using the command zeros(2,1) because SymPy 0.7.1, installed on my machine, complains that "zeros() takes exactly one argument", though the wiki suggests otherwise. Maybe this command is only for the git version.

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• How can I spot subtle Lisp syntax mistakes?

  - by Marius Andersen

  I'm a newbie playing around with Lisp (actually, Emacs Lisp). It's a lot of fun, except when I seem to run into the same syntax mistakes again and again. For instance, here's something I've encountered several times. I have some cond form, like (cond ((foo bar) (qux quux)) ((or corge (grault warg)) (fred) (t xyzzy))) and the default clause, which returns xyzzy, is never carried out, because it's actually nested inside the previous clause: (cond ((foo bar) (qux quux)) ((or corge (grault warg)) (fred)) (t xyzzy)) It's difficult for me to see such errors when the difference in indentation is only one space. Does this get easier with time? I also have problems when there's a large distance between the (mal-)indented line and the line it should be indented against. let forms with a lot of complex bindings, for example, or an unless form with a long conditional: (defun test () (unless (foo bar (qux quux) (or corge (grault warg) (fred)))) xyzzy) It turns out xyzzy was never inside the unless form at all: (defun test () (unless (foo bar (qux quux) (or corge (grault warg) (fred))) xyzzy)) I auto-indent habitually and use parenthesis highlighting to avoid counting parentheses. For the most part it works like a breeze, but occasionally, I discover my syntax mistakes only by debugging. What can I do?

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• close other infowindows nicely.

  - by raklos

  Im currently doing this to create markers for my google map. function createMarker(posn, title, html) { var marker = new google.maps.Marker({ position: posn, title: title, draggable: false }); marker['infowindow'] = new google.maps.InfoWindow({ content: html }); infoWindows.push(marker['infowindow']); google.maps.event.addListener(marker, "click", function () { for (i = 0; i < infoWindows.length; i++) { infoWindows[i].close(); } this['infowindow'].open(map, this); }); return marker; } im not happy with the for loop, for closing the markers, i know something similar to this can be done by using one refernce: if (infowindow) infowindow.close(); the reason I am using code like above is because i am doing something like markers[myPoint]['infowindow'].open(map, markers[myPoint]); else where, (myPoint is a number). how can i avoid this for loop to close open infowindows and do it the nice way?

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• My method is too specific. How can I make it more generic?

  - by EricBoersma

  I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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