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  • Common optimization rules

    - by mafutrct
    This is a dangerous question, so let me try to phrase it correctly. Premature optimization is the root of all evil, but if you know you need it, there is a basic set of rules that should be considered. This set is what I'm wondering about. For instance, imagine you got a list of a few thousand items. How do you look up an item with a specific, unique ID? Of course, you simply use a Dictionary to map the ID to the item. And if you know that there is a setting stored in a database that is required all the time, you simply cache it instead of issuing a database request hundred times a second. I guess there are a few even more basic ideas. I am specifically not looking for "don't do it, for experts: don't do it yet" or "use a profiler" answers, but for really simple, general hints. If you feel this is an argumentative question, you probably misunderstood my intention.

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  • When is a Cocoa callback given controll?

    - by Kaspa
    Hi, I've been searching around the web for an answer to this one, but was unable to find an answer, on the other side I think it's something quite common thus there is a possibility I'm missing some keywords here. Anyhow, the problem is as follows: When is control given to a callback function in ObjC (iPhone)? Does it happen after control is given to a high up in the hierarchy class responsible for the runloop? Can it occur in the middle of another function call being executed? As an example, let's take the NSURLConnection, we don't know or can't predict when it's going to call didReceiveResponse or the other callback methods, can it be the case that didReceiveResponse get's called when I'm in the middle of another function? (highly doubt that but was unable to find information on callbacks wating for the end of the run loop) Cheers, Kaspa

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  • C# overloading with generics: bug or feature?

    - by TN
    Let's have a following simplified example: void Foo<T>(IEnumerable<T> collection, params T[] items) { // ... } void Foo<C, T>(C collection, T item) where C : ICollection<T> { // ... } void Main() { Foo((IEnumerable<int>)new[] { 1 }, 2); } Compiler says: The type 'System.Collections.Generic.IEnumerable' cannot be used as type parameter 'C' in the generic type or method 'UserQuery.Foo(C, T)'. There is no implicit reference conversion from 'System.Collections.Generic.IEnumerable' to 'System.Collections.Generic.ICollection'. If I change Main to: void Main() { Foo<int>((IEnumerable<int>)new[] { 1 }, 2); } It will work ok. Why compiler does not choose the right overload?

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  • Using Java, can I have one JVM spawn another, and then have the original one exit?

    - by CarlG
    I have a need to have a running JVM start another JVM and then exit. I'm currently trying to do this via Runtime.getRuntime().exec(). The other JVM starts, but my original JVM won't exit until the "child" JVM process stops. It appears that using Runtime.getRuntime().exec() creates a parent-child relationship between the processes. Is there some way to de-couple the spawned process so that the parent can die, or some other mechanism to spawn a process without any relationship to the creating process? Note that this seems exactly like this question: http://stackoverflow.com/questions/2566502/using-java-to-spawn-a-process-and-keep-it-running-after-parent-quits but the accepted answer there doesn't actually work, at least not on my system (Windows 7, Java 5 and 6). It seems that maybe this is a platform-dependent behavior. I'm looking for a platform independent way to reliably invoke the other process and let my original process die.

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  • averaging matrix efficiently

    - by user248237
    in Python, given an n x p matrix, e.g. 4 x 4, how can I return a matrix that's 4 x 2 that simply averages the first two columns and the last two columns for all 4 rows of the matrix? e.g. given: a = array([[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]) return a matrix that has the average of a[:, 0] and a[:, 1] and the average of a[:, 2] and a[:, 3]. I want this to work for an arbitrary matrix of n x p assuming that the number of columns I am averaging of n is obviously evenly divisible by n. let me clarify: for each row, I want to take the average of the first two columns, then the average of the last two columns. So it would be: 1 + 2 / 2, 3 + 4 / 2 <- row 1 of new matrix 5 + 6 / 2, 7 + 8 / 2 <- row 2 of new matrix, etc. which should yield a 4 by 2 matrix rather than 4 x 4. thanks.

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  • How does HTTP Analyzer works?

    - by Rampage
    Halo, i am interest in methods, which http analyzer uses to capture data. I would like to write program which saves emails sent via web based clients. The problem is https and HTTP Analyzer solves it, but i dont know how. I got one interesting answer on my question before, but it doesnt reveal as much as i would like to know. Programs like HTTP Analyzer can catch the HTTPS data because they insert themselves in the HTTPS stack. As a result, they get the data after it's generated but before it's being encrypted and put in IP packets. This is highly non-trivial. How it is possible to make? If you have any interesting articles solving this issue, please let me know.

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  • What program should I write to use up the 3,472 minutes on my iPhone 3GS?

    - by billmaya
    Something slightly off-topic but bear with me. I've got an iPhone 3GS that I use only for development and over the months I've accumulated 3,472 rollover minutes (my primary phone is an Android G-1). It seems a shame to let these minutes go to "waste." What cool iPhone app would you like to see that uses these minutes up in a productive, interesting, and possibly cool way. I'll code whichever suggestion has the highest vote, providing it's not illegal and doesn't violate Apple's SDK, and release it for free on the AppStore.

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  • jquery text area length count?

    - by Nimesh
    Hi All, I have a text area field where i need to provide information about the word count when the user enters some text in the field. Length of the field is supposed to be 500 Characters. Initialy it must show min characters:100 | 0 of 500 // 0 of 500 must be in red color and once the user enters come character need to update the count as well. Once the user reaches the count say the min character 100, i need to display min characters:100 | 100 of 500 // 100 of 500 must be in green color. How can i do this?? is there any plugin for the same??? let me know your thoughts on this.

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  • How to retain a row which is foreign key in another table and remove other duplicate rows?

    - by Mithril
    I have two table: A: id code 1 A1 2 A1 3 B1 4 B1 5 C1 6 C1 ===================== B: id Aid 1 1 2 4 (B doesn't contain the Aid which link to code C1) Let me explain the overall flow: I want to make each row in table A have different code(by delete duplicate),and I want to retain the Aid which I can find in table B.If Aid which not be saved in table B,I retain the id bigger one. so I can not just do something as below: DELETE FROM A WHERE id NOT IN (SELECT MAX(id) FROM A GROUP BY code, ) I can get each duplicate_code_groups by below sql statement: SELECT code FROM A GROUP BY code HAVING COUNT(*) > 1 Is there some code in sql like for (var ids in duplicate_code_groups){ for (var id in ids) { if (id in B){ return id } } return max(ids) } and put the return id into a idtable?? I just don't know how to write such code in sql. then I can do DELETE FROM A WHERE id NOT IN idtable

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  • CMD Execption Handling C/C++

    - by ciyo
    I will use some CMD commands in my program and these commands might throw some exceptions. And as you know, when an exception accours, CMD writes its own error message the screen. But, I want to write my own error message. My question is this: Is there a way to block CMD messages and write only my own error messages? P.S. This is not a complex program. It executes CMD commands using System(). Example: Let's say, the user can rename and copy any files in the program. As you know, if the user does not enter file's path properly, an error message is showed on the screen. And I want that this error message never appears on the screen. Only my own error message is showed. Thank you!

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  • Facebook "Like" on iPhone/iPad

    - by half_brick
    Has anyone implemented facebook "Like" on iPhone/iPad? I've done general Facebook Connect implementation before, but it appears they're phasing that out in favour of OAuth and the Graph API? We're trying to give users the ability to "Like" items of content in the app. Each item of content has a corresponding URL for its representation on the website. Will it be possible to implement this kind of functionality (without implementing anything on the server side)? And is there a library that will let us do this easily? Thanks

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  • How do I make a project built into a downloadable Cd?

    - by Dcurvez
    hi all I just got finished making my first project in visual studio 2008. what I want to do is put it on a CD and let another person run it. I went to the clean and build and publish and all went well. When I took it to my friends house to put it on her computer..i never got a "download" and "install" screen. We were able to see it and use it on her computer (which is good cuz she doesnt have Visual on her machine) but I wanted her to be able to use it without keeping the CD in the drive. Is there some setup or something I have to do to make my program download and install? The whole shibang was all done with starting a new windows application..and then just adding windows forms to the original. Thanks :)

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  • Intersection between sets containing different types of variables

    - by Gacek
    Let's assume we have two collections: List<double> values List<SomePoint> points where SomePoint is a type containing three coordinates of the point: SomePoint { double X; double Y; double Z; } Now, I would like to perform the intersection between these two collections to find out for which points in points the z coordinate is eqal to one of the elements of values I created something like that: HashSet<double> hash = new HashSet<double>(points.Select(p=>p.Z)); hash.IntersectWith(values); var result = new List<SomePoints>(); foreach(var h in hash) result.Add(points.Find(p => p.Z == h)); But it won't return these points for which there is the same Z value, but different X and Y. Is there any better way to do it?

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  • ExtJS (4.0) dynamic / lazy loading

    - by Paul
    Given a border layout with a west (navigation) and a center region. Let say I click on topic A in the west region, I want to replace (replace as in 'delete last topic') the center region with 'extjs' program code named topic_a.js I succeed in loading with this code: dynamicPanel = new Ext.Component({ loader: { url: '/www/file.htm', renderer: 'html', autoLoad: true, scripts: true } }); var oMainContainer = Ext.getCmp('maincontainer'); oMainContainer.show(); oMainContainer.add(dynamicPanel); But calling this the second time 'adds' things up in the center region and of course fails short in 'deleting', what would be a good approach?

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  • Find all numbers that appear in each of a set of lists

    - by Ankur
    I have several ArrayLists of Integer objects, stored in a HashMap. I want to get a list (ArrayList) of all the numbers (Integer objects) that appear in each list. My thinking so far is: Iterate through each ArrayList and put all the values into a HashSet This will give us a "listing" of all the values in the lists, but only once Iterate through the HashSet 2.1 With each iteration perform ArrayList.contains() 2.2 If none of the ArrayLists return false for the operation add the number to a "master list" which contains all the final values. If you can come up with something faster or more efficient, funny thing is as I wrote this I came up with a reasonably good solution. But I'll still post it just in case it is useful for someone else. But of course if you have a better way please do let me know.

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  • How do I obtain an HtmlHelper<TModel> instance for a model in ASP.NET MVC?

    - by DanM
    Let's say I have an Index view. The model I pass in is actually a collection of models, so the Html property is of type HtmlHelper<List<MyModel>>. If I want to call extension methods (e.g., Display() or DisplayFor() on the individual items in the list, however, I think I need to obtain an HtmlHelper<MyModel>. But how? I tried using the HtmlHelper<TModel> constructor, which looks like this: HtmlHelper<TModel>(ViewContext, IViewDataContainer) But I'm not having any luck with that. I don't know how to obtain the IViewDataContainer for the item, and the documentation on these things is very sparse. A lot of magic apparently happens when I do... return View(List<MyModel>); ...in my controller. How do I recreate that magic on individual items in a list/collection?

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  • C#, working with files, "Unauthorized Access"?

    - by Rob
    Hi, I'm learning about opening and saving files with C# and it seems that vista won't let my program save to a file on the root of C:\ , unless I run it in administrator mode. Any ideas how to allow my program to play around with whatever files it wants? Thanks! string name; private void button2_Click(object sender, EventArgs e) ///// OPEN ///// { if (openFileDialog1.ShowDialog() == DialogResult.OK) { name = openFileDialog1.FileName; textBox1.Clear(); textBox1.Text = File.ReadAllText(name); textBox2.Text = name; } } private void button1_Click(object sender, EventArgs e) ///// SAVE ///// { File.WriteAllText(name, textBox1.Text); }

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  • Passing arguments to a python service

    - by Grim
    Hi, I need some help with a python service. I have a service written in Python. What I need to do is to pass it some arguments. Let me give you an example to explain it a bit better. Lets say I have a service, that does nothing but writes something to a log. I'd like to write the same thing into the log several times, so I use a loop. I would like to pass the counter for the loop when I start the service, but I have no idea how. I start the service with: win32serviceutil.HandleCommandLine(WinService) I'm looking for something like win32serviceutil.HandleCommandLine(WinService,10) I don't really care how its done, as long as I can pass arguments to it. Have been trying to get this to work for the better part of the day with no luck. Also, the service isn't run directly, but is imported and then run from there.

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  • What could cause a returning function to crash? C++

    - by JeanOTF
    So I have been debugging this error for hours now. I writing a program using Ogre3d relevant only because it doesn't load symbols so it doesn't let me stack trace which made finding the location of the crash even harder. So, write before I call a specific function I print out "Starting" then I call the function and immediately after I print "Stopping". Throughout the function I print out letters A-F where F is printed right before the function returns (one line above the last '}') The weird thing is when the crash occurs it is after the 'F' is printed but there is no 'Stopping'. Does this mean that the crash is happening in between somewhere? The only thing I can think of is something going wrong during the deallocation of some of the memory allocated during the function. I've never had anything happen like this, I will keep checking to make sure it's going wrong where I think it is.

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  • Allow users to enter a variable length list of items in asp.net form

    - by EJB
    I need to let my users enter a variable length list of items into something that looks like a grid view (or a series of standard text boxes stacked vertically). Each item could be a few characters or a few hundred characters long, and I just want them to enter a "sentence", and then tab to the next row, and always having another blank one ready to go at the bottom of the list. I don't want to save any data to my SQL Server DB until they enter the entire list and then click on a "save all" button. When they hit the "save all" button they will be given a preview screen where the data will be presented as standard HTML ordered list. If they confirm/save, then each row of the grid will then be saved as a separate row into my SQL Server database (with an index to remember the order). What ASP.Net (or Jquery/javascript) UI control would be the best to use in this situation?

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  • Why does Perl allow mutual "use" relationships between modules?

    - by Haiyuan Zhang
    Let's say there are two modules that mutually use each other: package a; use b; sub p {} 1; package b; use a; 1; I think that it is systematically wrong to write code like the above, because the two modules will endlessly copy each other's code to themselves, but I can successfully run the following code, which makes me very surprised. Could any of you explain all of this to me? #! /usr/bin/perl use a; a->p();

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  • Hiding "Print to file" in a Java print dialog

    - by Carl Smotricz
    I'm maintaining this Swing app that has a "print" option. Users need to be kept from interacting in any way with the underlying file system, but the print dialog offers "print to file" as one printer, and that of course allows selecting a directory and file from the file system. Is there a painless way to override/modify the print dialog to hide the "to file" printer from this dialog? I understand the API will let me do this piecemeal but I'd rather not have to re-create most of the dialog GUI and functionality to do this.

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  • When to save a variable in viewstate?

    - by Umut
    Hi, I have searched the web for the answer and saw that mostly variables are saved in viewstate on page.prerender event. However, when I save a variable in viewstate on prerender or load events, how can it store the changed value of the variable? Let's say, after page load, user clicked a button and the value of the variable was changed in onClick event of the button. Then the postback event raised since the button was clicked. According to me, the new value should have been lost and cannot be saved in the viewstate if I save the variable in the viewstate only in prerender event. Shouldn't I save the variable in the viewstate just before the postback event rises? Am I wrong? If so, how can viewstate store the new value of the variable? Thanks for the answer in advance..

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  • Timeout not working in SQL Connection

    - by carlos
    I have this simple code to test that a DB is ready: Function testlocalcon() As Boolean Dim constr As String = _clconstr Try Using t As New SqlConnection() constr = constr & " ; Connect Timeout=1" If Not t.State = Data.ConnectionState.Open Then t.ConnectionString = constr t.Open() If t.State = Data.ConnectionState.Open Then Return True Else Return False End If Else Return True End If End Using Catch ex As Exception Return False End Try End Function I do not want to execute a query, just to check the connection, but no matter what the time out parameter is ignored. I search here (Stackoverflow) and internet and found nothing in how to fix this. Any one else have this problem? Or, are there any other ideas on how to let the application know that the DB is ready?

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  • Count Clicks in excel

    - by rockbala
    Hi, Can some one recommend any free program which counts the number of clicks Clicked inside a cell. For Example Imagine something like Spreadsheet I click on A1 cell the value shows 1 Then I click A1 cell again the value shows 2 and so on If I click A3 cell somewhere in between the click count on Cell A3 shows 1 and so on If something like this can be achieved as a macro with in excel (2003 please) please suggest or any other free program that you might be aware about, please do let me know. I appreciate all your help and thank you in advance. rockbala

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