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  • C#/LINQ: How to define generically a keySelector for a templated class before calling OrderBy

    - by PierrOz
    Hi Folks, I have the following class defined in C# class myClass<T,U> { public T PropertyOne { get; set; } public U PropertyTwo { get; set; } } I need to write a function that reorder a list of myClass objects and takes two other parameters which define how I do this reorder: does my reordering depend on PropertyOne or PropertyTwo and is it ascending or descending. Let's say this two parameters are boolean. With my current knowledge in LINQ, I would write: public IList<myClass<T,U>> ReOrder(IList<myClass<T,U>> myList, bool usePropertyOne, bool ascending) { if (usePropertyOne) { if (ascending) { return myList.OrderBy(o => o.PropertyOne).ToList(); } else { return myList.OrderByDescending(o => o.PropertyOne).ToList(); } } else { if (ascending) { return myList.OrderBy(o => o.PropertyTwo).ToList(); } else { return myList.OrderByDescending(o => o.PropertyTwo).ToList(); } } } What could be a more efficient/elegant way to do that ? How can I declare the Func,TResult keySelector object to reuse when I call either OrderBy or OrderByDescending? I'm interesting in the answer since in my real life, I can have more than two properties.

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  • Jquery if statement help

    - by mtwallet
    Hi. I want to know how to correctly write an if statement with jquery. I have a bunch of div's with an anchor in each that when clicked expands the the div's width using toggleClass. This works fine but I want to write an if statement that checks to see if the other div's have the same class applied, if so contract that div, then expand the next div (hope that makes sense), my code so far: HTML: <div class="content-block"> <h2>Title</h2> <p>Content...</p> <a class="expand" href="#">Expand View</a> </div> <div class="content-block"> <h2>Title</h2> <p>Content...</p> <a class="expand" href="#">Expand View</a> </div> <div class="content-block"> <h2>Title</h2> <p>Content...</p> <a class="expand" href="#">Expand View</a> </div> <div class="content-block"> <h2>Title</h2> <p>Content...</p> <a class="expand" href="#">Expand View</a> </div> JQUERY: $(document).ready(function(){ $('a.expand').click(function(){ $(this).parent('.content-block').toggleClass('wide'); }); });

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  • Asynchronous event loop design and issues.

    - by Artyom
    Hello, I'm designing event loop for asynchronous socket IO using epoll/devpoll/kqueue/poll/select (including windows-select). I have two options of performing, IO operation: Non-blocking mode, poll on EAGAIN Set socket to non-blocking mode. Read/Write to socket. If operation succeeds, post completion notification to event loop. If I get EAGAIN, add socket to "select list" and poll socket. Polling mode: poll and then execute Add socket to select list and poll it. Wait for notification that it is readable writable read/write Post completion notification to event loop of sucseeds To me it looks like first would require less system calls when using in normal mode, especially for writing to socket (buffers are quite big). Also it looks like that it would be possible to reduce the overhead over number of "select" executions, especially it is nice when you do not have something that scales well as epoll/devpoll/kqueue. Questions: Are there any advantages of the second approach? Are there any portability issues with non-blocking operations on sockets/file descriptors over numerous operating systems: Linux, FreeBSD, Solaris, MacOSX, Windows. Notes: Please do not suggest using existing event-loop/socket-api implementations

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  • bing search api ajax does not work

    - by jhon
    Hi guys, I want to use the Bing's search api with javascript. Actually, I want the user to write something and query Bing in order to get just images. so, I tried it using ajax. If I try the url http://api.search.live.net/xml.aspx?Appid=[YOURAPIKEY]&sources=image&query=home directly (with the browser) I do get an xml document. but if I use XMLHttpRequest it does not work. <html> <body> <script> var xhr = new XMLHttpRequest(); var url="http://api.search.live.net/xml.aspx?Appid=[YOURAPIKEY]&sources=image&query=home" xhr.open("GET", url, true ); xhr.onreadystatechange=function(){ /*if( xhr.readyState == 4 && xhr.status == 200) { document.write( xhr.responseText ); }*/ alert( xhr.readyState +" "+xhr.status +xhr.statusText +xhr); }; xhr.send(null); </script> </body> </html> Questions: 1) why does the code from above does not work? 2) any other way to do this without XMLHttpRequest? thanks. btw. I'm just interested in fix this for Firefox and without external libraries (jquery and so on).

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  • Excel VBA - export to UTF-8

    - by Tom
    The macro I created works fine, I just need to sort out the saving business. Now I get a popup asking me where to save it, but I would like it to save it under a default name and path AND encoded in UTF-8. This is my full code I use, the bottom part saves the document I presume. Public Sub ExportToTextFile(FName As String, Sep As String, SelectionOnly As Boolean, AppendData As Boolean) Dim WholeLine As String Dim fnum As Integer Dim RowNdx As Long Dim ColNdx As Integer Dim StartRow As Long Dim EndRow As Long Dim StartCol As Integer Dim EndCol As Integer Dim CellValue As String Dim teller As Integer 'Teller aangemaakt ter controle voor het aantal velden 'teller = 1 Application.ScreenUpdating = False On Error GoTo EndMacro: fnum = FreeFile If SelectionOnly = True Then With Selection StartRow = .Cells(1).Row StartCol = .Cells(26).Column EndRow = .Cells(.Cells.Count).Row EndCol = .Cells(.Cells.Count).Column End With Else With ActiveSheet.UsedRange StartRow = .Cells(1).Row StartCol = .Cells(26).Column EndRow = .Cells(.Cells.Count).Row EndCol = .Cells(26).Column End With End If If AppendData = True Then Open FName For Append Access Write As #fnum Else Open FName For Output Access Write As #fnum End If For RowNdx = StartRow To EndRow WholeLine = "" For ColNdx = StartCol To EndCol If Cells(RowNdx, ColNdx).Value = "" Then CellValue = "" Else CellValue = Cells(RowNdx, ColNdx).Value End If WholeLine = WholeLine & CellValue & Sep Next ColNdx WholeLine = Left(WholeLine, Len(WholeLine) - Len(Sep)) Print #fnum, WholeLine, "" 'Print #fnum, teller, WholeLine, "" 'teller = teller + 1 Next RowNdx EndMacro: On Error GoTo 0 Application.ScreenUpdating = True Close #fnum End Sub Sub Dump4Mini() Dim FileName As Variant Dim Sep As String FileName = Application.GetSaveAsFilename(InitialFileName:=Blank, filefilter:="Text (*.txt),*.txt") If FileName = False Then Exit Sub End If Sep = "|" If Sep = vbNullString Then Exit Sub End If Debug.Print "FileName: " & FileName, "Separator: " & Sep ExportToTextFile FName:=CStr(FileName), Sep:=CStr(Sep), SelectionOnly:=False, AppendData:=False End Sub

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  • Creating a REST client API using Reactive Extensions (Rx)

    - by Jonas Follesø
    I'm trying to get my head around the right use cases for Reactive Extensions (Rx). The examples that keeps coming up are UI events (drag and drop, drawing), and suggestions that Rx is suitable for asynchronous applications/operations such as web service calls. I'm working on an application where I need to write a tiny client API for a REST service. I need to call four REST end-points, three to get some reference data (Airports, Airlines, and Statuses), and the fourth is the main service that will give you flight times for a given airport. I have created classes exposing the three reference data services, and the methods look something like this: public Observable<Airport> GetAirports() public Observable<Airline> GetAirlines() public Observable<Status> GetStatuses() public Observable<Flights> GetFlights(string airport) In my GetFlights method I want each Flight to hold a reference the Airport it's departing from, and the Airline operating the flight. To do that I need the data from GetAirports and GetAirlines to be available. My initial thinking was something like this: Write a Rx Query that will Subscribe on the three reference services (Airports, Airlines and Statuses) Add results into a Dictionary (airline code and Airline object) When all three GetAirports, GetAirlines and GetStatuses are complete, then return the GetFlights IObservable. Is this a reasonable scenario for Rx? I'm developing on the Windows Phone 7, so I'm not sure if there are major differences in the Rx implementations across the different platforms.

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  • unistd.h related problem when compiling bison & flex program under vc++

    - by Eric
    I'm using bison & flex (downloaded via cygwin) with vc++. When I compile the program I got an error: ...: fatal error C1083: Cannot open include file: 'unistd.h': No such file or directory The corresponding code in the flex-generated file is: #ifndef YY_NO_UNISTD_H /* Special case for "unistd.h", since it is non-ANSI. We include it way * down here because we want the user's section 1 to have been scanned first. * The user has a chance to override it with an option. */ /* %if-c-only */ #include <unistd.h> /* %endif */ /* %if-c++-only */ /* %endif */ #endif If I define YY_NO_UNISTD_H in the flex file(.l) this error will disappear, but I get several other errors: ...: error C2447: '{' : missing function header (old-style formal list?) ...: warning C4018: '<' : signed/unsigned mismatch ...: error C3861: 'isatty': identifier not found How can I fix this problem? All these errors occur in the flex-generated scanner. I know it's because unistd.h doesn't exist in windows. Do I have to write my own unistd.h? If so how to write it in order to eliminate those errors?

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  • How do I overwrite a file currently being read by Python

    - by Brian
    Hi guys, I am not too sure the best way to word this, but what I want to do, is read a pdf file, make various modifications, and save the modified pdf over the original file. As of now, I am able to save the modified pdf to a separate file, but I am looking to replace the original, not create a new file. Here is my current code: from pyPdf import PdfFileWriter, PdfFileReader output = PdfFileWriter() input = PdfFileReader(file('input.pdf', 'rb')) blank = PdfFileReader(file('C:\\BLANK.pdf', 'rb')) # Copy the input pdf to the output. for page in range(int(input.getNumPages())): output.addPage(input.getPage(page)) # Add a blank page if needed. if (input.getNumPages() % 2 != 0): output.addPage(blank.getPage(0)) # Write the output to pdf. outputStream = file('input.pdf', 'wb') output.write(outputStream) outputStream.close() If i change the outputStream to a different file name, it works fine, I just cant save over the input file because it is still being used. I have tried to .close() the stream, but it was giving me errors as well. I have a feeling this has a fairly simple solution, I just haven't had any luck finding it. Thanks!

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  • How do I make software that preserves database integrity and correctness?

    - by user287745
    I have made an application project in Visual Studio 2008 C#, SQL Server from Visual Studio 2008. The database has like 20 tables and many fields in each. I have made an interface for adding deleting editing and retrieving data according to predefined needs of the users. Now I have to Make to project into software which I can deliver to my professor. That is, he can just double click the icon and the software simply starts. No Visual Studio 2008 needed to start the debugging. The database will be on one powerful computer (dual core latest everything Windows XP) and the user will access it from another computer connected using LAN. I am able to change the connection string to the shared database using Visual Studio 2008/ debugger whenever the server changes but how am I supposed to do that when it's software? There will by many clients. Am I supposed to give the same software to every one, so they all can connect to the database? How will the integrity and correctness of the database be maintained? I mean the db.mdf file will be in a folder which will be shared with read and write access. So it's not necessary that only one user will write at a time. So is there any coding for this or?

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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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  • Wpf binding with nested properties

    - by byte
    ViewModel I have a property of type Member called KeyMember. The 'Member' type has an ObservableCollection called Addresses. The Address is composed of two strings - street and postcode . View I have a ListBox whose item source need to be set to ViewModels's KeyMember property and it should display the Street of all the Past Addresses in the collection. Question My ViewModel and View relationship is established properly. I am able to write a data template for the above simple case as below <ListBox ItemsSource="{Binding KeyMember.Addresses}"> <ListBox.ItemTemplate> <DataTemplate DataType="Address"> <TextBlock Text="{Binding Street}"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> How would I write the DataTemplate if I change KeyMember from type Member to ObservableCollection< Member assuming that the collection has only one element. PS: I know that for multiple elements in collection, I will have to implement the Master-Detail pattern/scenario.

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  • Problem pulling data from website in .NET and C#

    - by Cptcecil
    I have written a web scraping program to go to a list of pages and write all the html to a file. The problem is that when I pull a block of text some of the characters get written as '?'. How do I pull those characters into my text file? Here is my code: string baseUri = String.Format("http://www.rogersmushrooms.com/gallery/loadimage.asp?did={0}&blockName={1}", id.ToString(), name.Trim()); // our third request is for the actual webpage after the login. HttpWebRequest request = (HttpWebRequest)WebRequest.Create(baseUri); request.Method = "GET"; request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1)"; //get the response object, so that we may get the session cookie. HttpWebResponse response = (HttpWebResponse)request.GetResponse(); StreamReader reader = new StreamReader(response.GetResponseStream()); // and read the response string page = reader.ReadToEnd(); StreamWriter SW; string filename = string.Format("{0}.txt", id.ToString()); SW = File.AppendText("C:\\Share\\" + filename); SW.Write(page); reader.Close(); response.Close();

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  • Creating a Hello World library function in assembly and calling it from C#

    - by Filip Ekberg
    Let's say we use NASM as they do in this answer: how to write hellow world in assembly under windows. I got a couple of thoughts and questions regarding assembly combined with c# or any other .net languages for that matter. First of all I want to be able to create a library that has the following function HelloWorld that takes this parameter: Name In C# the method signature would looke like this: void HelloWorld(string name) and it would print out something like Hello World from name I've searched around a bit but can't find that much good and clean material for this to get me started. I know some basic assembly from before mostly gasthough. So any pointers in the right direction is very much apprechiated. To sum it up Create a function in ASM ( NASM ) that takes one or more parameters Compile and create a library of the above functionality Include the library in any .net language Call the included library function Bonus features How does one handle returned values? Is it possible to write the ASM-method inline? When creating libraries in assembly or c, you do follow a certain "pre defined" way, the c calling convetion, correct?

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  • Can PHP dissect its own syntax?

    - by Nathan Long
    Can PHP dissect its own syntax? For example, I'd like to write a function that takes in an input like $object->attribute and says to itself: OK, he's giving me $foo->bar, which means he must think that $foo is an object that has a property called bar. Before I try accessing bar and potentially get a 'Trying to get property of non-object' error, let me check whether $foo is even an object. The end goal is to echo a value if it is set, and fail silently if not. I want to avoid repetition like this: <input value="<? if(is_object($foo) && is_set($foo->bar)){ echo $foo->bar; }?> "/> ...and to avoid writing a function that does the above, but has to have the object and attribute passed in separately, like this: <input value="<? echoAttribute($foo,'bar') ?>" /> ...but to instead write something which: preserves the object-attribute syntax is flexible: can also handle array keys or regular variables Like this: <input value="<? echoIfSet($foo->bar); ?> /> <input value="<? echoIfSet($baz['buzz']); ?> /> <input value="<? echoIfSet($moo); ?> /> But this all depends on PHP being able to tell me "what kind of thing am I asking for when I say $object->attribute or $array[$key]", so that my function can handle each according to its own type. Is this possible?

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  • Writing a JavaScript zip code validation function

    - by mkoryak
    I would like to write a JavaScript function that validates a zip code, by checking if the zip code actually exists. Here is a list of all zip codes: http://www.census.gov/tiger/tms/gazetteer/zips.txt (I only care about the 2nd column) This is really a compression problem. I would like to do this for fun. OK, now that's out of the way, here is a list of optimizations over a straight hashtable that I can think of, feel free to add anything I have not thought of: Break zipcode into 2 parts, first 2 digits and last 3 digits. Make a giant if-else statement first checking the first 2 digits, then checking ranges within the last 3 digits. Or, covert the zips into hex, and see if I can do the same thing using smaller groups. Find out if within the range of all valid zip codes there are more valid zip codes vs invalid zip codes. Write the above code targeting the smaller group. Break up the hash into separate files, and load them via Ajax as user types in the zipcode. So perhaps break into 2 parts, first for first 2 digits, second for last 3. Lastly, I plan to generate the JavaScript files using another program, not by hand. Edit: performance matters here. I do want to use this, if it doesn't suck. Performance of the JavaScript code execution + download time. Edit 2: JavaScript only solutions please. I don't have access to the application server, plus, that would make this into a whole other problem =)

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  • How to minor updates to Drupal-6 with shared hosting

    - by marty.fried
    I've got Drupal working on a shared host, and I uploaded some modules from my home system successfully, but I've got the message that there is a security update for my version, and I should update immediately. I'm not sure how I'm supposed to do that. It seems like the update is an entire new installation. I originally installed it using the hosting company's installer, Fantastico. Should I simply over-write the existing installation with the new files? Or ignore the message? I realize I shouldn't over-write the sites folder, or anything I've modified. The instructions that come with the download seem to be for a major version upgrade, and are way too much trouble for frequent security updates. Searching Drupal's site shows many other methods, but no indication of anything official. And some were ridiculously error-prone, and not really useful. I don't have shell access to the hosting site, although I can pay extra to get it if I really need to. Or, maybe I can clone the site on my local Linux system, do the update using a script, then upload the whole thing. Does anyone have experience with this situation?

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  • Testing Finite State Machines

    - by Pondidum
    I have inherited a large and firaly complex state machine at work. It has 31 possbile states to be in. It has the following inputs: Enum: Current State (so 0 - 30) Enum: source (currently only 2 entries) Boolean: Request Boolean: type Enum: Status (3 states) Enum: Handling (3 states) Boolean: Completed The 31 States are really needed (big business process). Breaking into seperate state machines doesnt seem feasable - each state is distinct. I have written tests for one set of inputs (the most common set), with one test per input (all inputs constant, except for the State input): [Subject("Application Process States")] public class When_state_is_meeting2Requested : AppProcessBase { Establish context = () => { //Setup.... }; Because of = () => process.Load(jas, vac); It Current_node_should_be_meeting2Requested = () => process.CurrentNode.ShouldBeOfType<meetingRequestedNode>(); It Can_move_to_clientDeclined = () => Check(process, process.clientDeclined); It Can_move_to_meeting1Arranged = () => Check(process, process.meeting1Arranged); It Can_move_to_meeting2Arranged = () => Check(process, process.meeting2Arranged); It Can_move_to_Reject = () => Check(process, process.Reject); It Cannot_move_to_any_other_state = () => AllOthersFalse(process); } As no one is entirely sure on what the output should be for each state and set of inputs i have been starting to write tests for it, however on calculation i will need to write 4320 ( 30*2*2*2*3*3*2 ) tests for it. Does anyone have any suggestions on how i should go about testing this?

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  • WebRequest using SSL

    - by pm_2
    I have the following code to retrieve a file using FTP (which works fine). FtpWebRequest request = (FtpWebRequest)WebRequest.Create(svrPath); request.KeepAlive = true; request.UsePassive = true; request.UseBinary = true; request.Method = WebRequestMethods.Ftp.DownloadFile; request.Credentials = new NetworkCredential(uname, passw); using (FtpWebResponse response = (FtpWebResponse)request.GetResponse()) using (Stream responseStream = response.GetResponseStream()) using (StreamReader reader = new StreamReader(responseStream)) using (StreamWriter destination = new StreamWriter(destinationFile)) { destination.Write(reader.ReadToEnd()); destination.Flush(); } However, when I try to do this using SSL, I am unable to access the file, as follows: FtpWebRequest request = (FtpWebRequest)WebRequest.Create(svrPath); request.KeepAlive = true; request.UsePassive = true; request.UseBinary = true; // The following line causes the download to fail request.EnableSsl = true; request.Method = WebRequestMethods.Ftp.DownloadFile; request.Credentials = new NetworkCredential(uname, passw); using (FtpWebResponse response = (FtpWebResponse)request.GetResponse()) using (Stream responseStream = response.GetResponseStream()) using (StreamReader reader = new StreamReader(responseStream)) using (StreamWriter destination = new StreamWriter(destinationFile)) { destination.Write(reader.ReadToEnd()); destination.Flush(); } Can anyone tell me why the latter would not work?

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  • How to use Profile in asp.net?

    - by Phsika
    i try to learn asp.net Profile management. But i added below xml firstName,LastName and others. But i cannot write Profile. if i try to write Profile property. drow my editor Profile : Error 1 The name 'Profile' does not exist in the current context C:\Documents and Settings\ykaratoprak\Desktop\Security\WebApp_profile\WebApp_profile\Default.aspx.cs 18 13 WebApp_profile How can i do that? <authentication mode="Windows"/> <profile> <properties> <add name="FirstName"/> <add name="LastName"/> <add name="Age"/> <add name="City"/> </properties> </profile> protected void Button1_Click(object sender, System.EventArgs e) { Profile.FirstName = TextBox1.Text; Profile.LastName = TextBox2.Text; Profile.Age = TextBox3.Text; Profile.City = TextBox4.Text; Label1.Text = "Profile stored successfully!<br />" + "<br />First Name: " + Profile.FirstName + "<br />Last Name: " + Profile.LastName + "<br />Age: " + Profile.Age + "<br />City: " + Profile.City; }

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  • Starting a process in one HTTP call and getting results in another

    - by KillianDS
    Hi, I'm writing a very simple testing framework for my application, the design isn't perfect, but I don't have time to write something more complex. Essentially, I have a client and server-application, on my server I want a small python web server to start the server application with given test sequences on a GET or POST call. Also, the application prints some testdata to stderr which I'd like to catch and return in another HTTP call. At the moment I have this: from subprocess import Popen, PIPE from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer p = None class MyHandler(BaseHTTPRequestHandler): def do_GET(self): global p if self.path.endswith("start/"): p = Popen(["./bin/Release/simplex264","BBB-360","127.0.0.1"], stderr=PIPE) print 'started' return elif self.path.endswith("getResults/"): self.wfile.write(p.stderr.read()) return self.send_error(404,'File Not Found: %s' % self.path) def main(): try: server = HTTPServer(('localhost', 9876), MyHandler) print 'Started server...' server.serve_forever() except KeyboardInterrupt: print 'Shutting down...' server.socket.close() if __name__ == '__main__': main() Which 'works', except for one part, when I try to open http://localhost:9876/start/, it does not return before the process ended. However, the 'started' appears in my shell immediately (I added this because I thought the Popen call would only return after execution). I do not know the perfect inner workings of Popen and BaseHTTPRequestHandler however and do not really know where it goes wrong. Is there any way to make this work asynchronously?

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  • tips for fixing bad coding/dev habits ?

    - by dfafa
    i want to become a better coder....so i have decided to sign up for computing science program...maybe a formal education can assist me. i started working on smaller projects to learn but currently i have really bad coding/dev habits which is hindering my productivity as the codebase increases.... i have highlighted them and perhaps someone could make suggestions (or redirect to resources) or a more efficient method. most stuff that i made in the past were web apps. i usually develop with putty + nano...i just love the minimalist feel i use winscp and develop directly on my private web server...too lazy to do it on localhost and upload it later. i dont use subversion control...which one do i need ? sometimes ctrl +z doesn't work well. when i run out of ideas for naming variable, i use swear words instead. i swear a lot when i get stuck....how to deal with anger issue ? my codes look ugly with comments everywhere. would rather use procedural coding finds "thinking" in OO difficult and time consuming i "write first think later". refactors code only if i am getting paid for it. dislikes configuring linux distro, Apache, MySQL, scaling, designing graphics and layouts. does not like writing tests likes working alone. does not like sharing codes. has an econ degree dislikes reading other people's code would rather write it on my own it seems my only true desire is to translate my ideas to a working prototype as fast as possible....it seems like i am very uninterested in the other details...could it be that i am not cut out to be a coder after all ? is going back to study comp sci a bad idea ?

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  • Groovy / Scala / Java under the hood

    - by Jack
    I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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  • Naming multi-instance performance counters in .NET

    - by Roger Lipscombe
    Most multiple instance performance counters in Windows seem to automatically(?) have a #n on the end if there's more than one instance with the same name. For example: if, in Perfmon, you look under the Process category, you'll see: ... dwm explorer explorer#1 ... I have two explorer.exe processes, so the second counter has #1 appended to its name. When I attempt to do this in a .NET application: I can create the category, and register the instance (using the PerformanceCounterCategory.Create that takes a CounterCreationDataCollection). I can open the counter for write and write to it. When I open the counter a second time, it opens the same counter. This means that I have two applications fighting over the counters. The documentation for PerformanceCounter.InstanceName states that # is not allowed in the name. So: how do I have multiple-instance performance counters that are actually multiple instance? And where the second (and subsequent) instances get #n appended to the name? That is: I know that I can put the process ID (e.g.) on the instance name. This works, but has the unfortunate side effect that restarting the process results in a new PID, and Perfmon continues monitoring the old counter.

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  • Is it possible to store pointers in shared memory without using offsets?

    - by Joseph Garvin
    When using shared memory, each process may mmap the shared region into a different area of their address space. This means that when storing pointers within the shared region, you need to store them as offsets of the start of the shared region. Unfortunately, this complicates use of atomic instructions (e.g. if you're trying to write a lock free algorithm). For example, say you have a bunch of reference counted nodes in shared memory, created by a single writer. The writer periodically atomically updates a pointer 'p' to point to a valid node with positive reference count. Readers want to atomically write to 'p' because it points to the beginning of a node (a struct) whose first element is a reference count. Since p always points to a valid node, incrementing the ref count is safe, and makes it safe to dereference 'p' and access other members. However, this all only works when everything is in the same address space. If the nodes and the 'p' pointer are stored in shared memory, then clients suffer a race condition: x = read p y = x + offset Increment refcount at y During step 2, p may change and x may no longer point to a valid node. The only workaround I can think of is somehow forcing all processes to agree on where to map the shared memory, so that real pointers rather than offsets can be stored in the mmap'd region. Is there any way to do that? I see MAP_FIXED in the mmap documentation, but I don't know how I could pick an address that would be safe.

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  • What do you use to play sound in iPhone games?

    - by zoul
    Hello! I have a performance-intensive iPhone game I would like to add sounds to. There seem to be about three main choices: (1) AVAudioPlayer, (2) Audio Queues and (3) OpenAL. I’d hate to write pages of low-level code just to play a sample, so that I would like to use AVAudioPlayer. The problem is that it seems to kill the performace – I’ve done a simple measuring using CFAbsoluteTimeGetCurrent and the play message seems to take somewhere from 9 to 30 ms to finish. That’s quite miserable, considering that 25 ms == 40 fps. Of course there is the prepareToPlay method that should speed things up. That’s why I wrote a simple class that keeps several AVAudioPlayers at its disposal, prepares them beforehand and then plays the sample using the prepared player. No cigar, still it takes the ~20 ms I mentioned above. Such performance is unusable for games, so what do you use to play sounds with a decent performance on iPhone? Am I doing something wrong with the AVAudioPlayer? Do you play sounds with Audio Queues? (I’ve written something akin to AVAudioPlayer before 2.2 came out and I would love to spare that experience.) Do you use OpenAL? If yes, is there a simple way to play sounds with OpenAL, or do you have to write pages of code? Update: Yes, playing sounds with OpenAL is fairly simple.

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