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• Preserving timestamps on Clojure .clj files when building shaded jar via Maven Shade Plugin

  - by Dereference

  When using the maven-shade-plugin to package our jar artifact that contained a few Clojure libs and some Java. We were using AOT compilation for our Clojure code. When we loaded the jar, it was having very slow load times. AOT compilation is supposed to help this quite a bit, but that wasn't what we were seeing. We noticed in java jar -verbose output that there was a lot of JVM__DEFINE_CLASS calls happening when Clojure classes were being loaded. This didn't make sense, since more of our Clojure code was AOT compiled to .class files. Turns out the maven-shade-plugin creates all new files, with new timestamps in the final artifact Clojure uses the timestamp information on a .clj file vs. a .class file, to determine if the file needs to be recompiled. The maven-shade-plugin was causing the .clj file and it's associated .class file to have the same timestamp, so Clojure always chose to dynamically recompile the source. The only workaround that we have been able to figure out, at this point, is to write a script that would re-open the shaded jar and bump the .clj file timestamps back to some time in the past, so that they wouldn't be equal to the timestamps of their associated .class files. Does anyone know of a better approach?

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• ESXi with software iSCSI

  - by jharley

  Has anyone had any luck using the swiSCSI driver on ESXi? Following the instructions from VMWare.com I get to the point where I have the iSCSI HBA showing up but no LUNs/targets are showing up. The iSCSI target is running on Solaris 10 update 5 and works with other initiators fine. The ESXi initiator (from the logs) sees the targets but just logs in and out of them every 2 - 5 seconds. We're using unauthenticated discovery, and over and over in /var/log/messages I see: iSCSI: bus 0 target 0 trying to establish session 0xb203f90 to portal 0, address 10.1.100.9 port 3260 group 1 iSCSI: bus 0 target 0 establish session 0xb203f90 #4848 to port 0, address 10.1.100.9 port 3260 group 1, alias data/ESXi iSCSI: session 0xb203f90 dropping after receiving unexpected opcode 0x60 iSCSI: session 0xb203f90 to data/ESXi dropped iSCSI: session 0xb203f90 to data/ESXi waiting 2 seconds before next login attempt The only other thing that seems out of wack is that my 'Recent Tasks' pane keeps filling with 'Browse Diagnostic Manager' events and /var/log/vmware/hostd.log is filled with messages like this up to two times per second: [2008-09-19 16:05:57.901 'TaskManager' 196621 info] Task Created: haTask-ha-host-vim.DiagnosticManager.browser-776 [2008-09-19 16:05:57.094 'TaskManager' 196621 info] Task Completed: haTask-ha-host-vim.DiagnosticManager.browser-766 Any help would be appreciated.

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• Omit return type in C++0x

  - by Clinton

  I've recently found myself using the following macro with gcc 4.5 in C++0x mode: #define RETURN(x) -> decltype(x) { return x; } And writing functions like this: template <class T> auto f(T&& x) RETURN (( g(h(std::forward<T>(x))) )) I've been doing this to avoid the inconvenience having to effectively write the function body twice, and having keep changes in the body and the return type in sync (which in my opinion is a disaster waiting to happen). The problem is that this technique only works on one line functions. So when I have something like this (convoluted example): template <class T> auto f(T&& x) -> ... { auto y1 = f(x); auto y2 = h(y1, g1(x)); auto y3 = h(y1, g2(x)); if (y1) { ++y3; } return h2(y2, y3); } Then I have to put something horrible in the return type. Furthermore, whenever I update the function, I'll need to change the return type, and if I don't change it correctly, I'll get a compile error if I'm lucky, or a runtime bug in the worse case. Having to copy and paste changes to two locations and keep them in sync I feel is not good practice. And I can't think of a situation where I'd want an implicit cast on return instead of an explicit cast. Surely there is a way to ask the compiler to deduce this information. What is the point of the compiler keeping it a secret? I thought C++0x was designed so such duplication would not be required.

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• Best implementation of Java Queue?

  - by Georges Oates Larsen

  I am working (In java) on a recursive image processing algorithm that recursively traverses the pixels of the image, outward from a center point. Unfortunately... That causes stack overflows, so I have decided to switch to a Queue-based algorithm. Now, this is all fine and dandy -- But considering the fact that its queue will be analyzing THOUSANDS of pixels in a very short amount of time, while constantly popping and pushing, WITHOUT maintaining a predictable state (It could be anywhere between length 100, and 20000); The queue implementation needs to have significantly fast popping and pushing abilities. A linked list seems attractive due to its ability to push elements unto its self without rearranging anything else in the list, but in order for it to be fast enough, it would need easy access to both its head, AND its tail (or second-to-last node if it were not doubly-linked). Sadly, though I cannot find any information related to the underlying implementation of linked lists in Java, so it's hard to say if a linked list is really the way to go... This brings me to my question... What would be the best implementation of the Queue interface in Java for what I intend to do? (I do not wish to edit or even access anything other than the head and tail of the queue -- I do not wish to do any sort of rearranging, or anything. On the flip side, I DO intend to do a lot of pushing and popping, and the queue will be changing size quite a bit, so preallocating would be inefficient)

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• How to iterate JPA collections in Google App engine

  - by palto

  Hi I use Google App Engine with datanucleus and JPA. I'm having a real hard time grasping how I'm supposed to read stuff from data store and pass it to JSP. If I load a list of POJOs with entitymanager and pass it to JSP, it crashes to org.datanucleus.exceptions.NucleusUserException: Object Manager has been closed. I understand why this is happening. Obviously because I fetch the list, close the entity manager and pass it to JSP, at which point it will fail because the list is lazy. How do I make the list NOT lazy without resorting to hacks like calling size() or something like that? Here is what I'm trying to do: @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setAttribute("parties", getParties()); RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/parties.jsp"); dispatcher.forward(req, resp); } private List<Party> getParties(){ EntityManager em = entityManagerProvider.get(); try{ Query query = em.createQuery("SELECT p FROM Party p"); return query.getResultList(); }finally{ em.close(); } }

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• Questions about the Backpropogation Algorithm

  - by Colemangrill

  I have a few questions concerning backpropogation. I'm trying to learn the fundamentals behind neural network theory and wanted to start small, building a simple XOR classifier. I've read a lot of articles and skimmed multiple textbooks - but I can't seem to teach this thing the pattern for XOR. Firstly, I am unclear about the learning model for backpropogation. Here is some pseudo-code to represent how I am trying to train the network. [Lets assume my network is setup properly (ie: multiple inputs connect to a hidden layer connect to an output layer and all wired up properly)]. SET guess = getNetworkOutput() // Note this is using a sigmoid activation function. SET error = desiredOutput - guess SET delta = learningConstant * error * sigmoidDerivative(guess) For Each Node in inputNodes For Each Weight in inputNodes[n] inputNodes[n].weight[j] += delta; // At this point, I am assuming the first layer has been trained. // Then I recurse a similar function over the hidden layer and output layer. // The prime difference being that it further divi's up the adjustment delta. I realize this is probably not enough to go off of, and I will gladly expound on any part of my implementation. Using the above algorithm, my neural network does get trained, kind of. But not properly. The output is always XOR 1 1 [smallest number] XOR 0 0 [largest number] XOR 1 0 [medium number] XOR 0 1 [medium number] I can never train the [1,1] [0,0] to be the same value. If you have any suggestions, additional resources, articles, blogs, etc for me to look at I am very interested in learning more about this topic. Thank you for your assistance, I appreciate it greatly!

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• Searching in graphs trees with Depth/Breadth first/A* algorithms

  - by devoured elysium

  I have a couple of questions about searching in graphs/trees: Let's assume I have an empty chess board and I want to move a pawn around from point A to B. A. When using depth first search or breadth first search must we use open and closed lists ? This is, a list that has all the elements to check, and other with all other elements that were already checked? Is it even possible to do it without having those lists? What about A*, does it need it? B. When using lists, after having found a solution, how can you get the sequence of states from A to B? I assume when you have items in the open and closed list, instead of just having the (x, y) states, you have an "extended state" formed with (x, y, parent_of_this_node) ? C. State A has 4 possible moves (right, left, up, down). If I do as first move left, should I let it in the next state come back to the original state? This, is, do the "right" move? If not, must I transverse the search tree every time to check which states I've been to? D. When I see a state in the tree where I've already been, should I just ignore it, as I know it's a dead end? I guess to do this I'd have to always keep the list of visited states, right? E. Is there any difference between search trees and graphs? Are they just different ways to look at the same thing?

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• Is this 2D array initialization a bad idea?

  - by Brendan Long

  I have something I need a 2D array for, but for better cache performance, I'd rather have it actually be a normal array. Here's the idea I had but I don't know if it's a terrible idea: const int XWIDTH = 10, YWIDTH = 10; int main(){ int * tempInts = new int[XWIDTH * YWIDTH]; int ** ints = new int*[XWIDTH]; for(int i=0; i<XWIDTH; i++){ ints[i] = &tempInts[i*YWIDTH]; } // do things with ints delete[] ints[0]; delete[] ints; return 0; } So the idea is that instead of newing a bunch of arrays (and having them placed in different places in memory), I just point to an array I made all at once. The reason for the delete[] (int*) ints; is because I'm actually doing this in a class and it would save [trivial amounts of] memory to not save the original pointer. Just wondering if there's any reasons this is a horrible idea. Or if there's an easier/better way. The goal is to be able to access the array as ints[x][y] rather than ints[x*YWIDTH+y].

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• asp.net mvc 2 - return JavaScript with View

  - by Tomaszewski

  Hi, using ASP.NET MVC 2 I have a navigation menu inside my Master Page. In the navigation menu, I am trying add a class to the that the current page relates to (i.e., home page will add class="active" to the Home button). I'm trying to consider scalability and the fact that I don't want to change individual pages if the navigation changes later. The only way I can think of doing this is: Add JavaScript to each individual View that will add the class when the DOM is ready Return JavaScript when return View() occurs on point (2), I am unsure how to do. Thusfar I have been doing the following in my controller: public ActionResult Index() { ViewData["messege"] = JavaScript("<script type='text/javascript' language='javascript'> $(document).ready(function () { console.log('hi hi hi'); }); </script>"); return View(); } but in my view, when I call: <%: ViewData["messege"] %> I get: System.Web.Mvc.JavaScriptResult as the result Would you guys have any ideas on How to solve the navigation menu probelem, other than the solutions I've listed return JavaScript along with your view from the Controller Thanks, in advanced!

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• Why is my Scala function returning type Unit and not whatever is the last line?

  - by Andy

  I am trying to figure out the issue, and tried different styles that I have read on Scala, but none of them work. My code is: .... val str = "(and x y)"; def stringParse ( exp: String, pos: Int, expreshHolder: ArrayBuffer[String], follow: Int ) var b = pos; //position of where in the expression String I am currently in val temp = expreshHolder; //holder of expressions without parens var arrayCounter = follow; //just counts to make sure an empty spot in the array is there to put in the strings if(exp(b) == '(') { b = b + 1; while(exp(b) == ' '){b = b + 1} //point of this is to just skip any spaces between paren and start of expression type if(exp(b) == 'a') { temp(arrayCounter) = exp(b).toString; b = b+1; temp(arrayCounter)+exp(b).toString; b = b+1; temp(arrayCounter) + exp(b).toString; arrayCounter+=1} temp; } } val hold: ArrayBuffer[String] = stringParse(str, 0, new ArrayBuffer[String], 0); for(test <- hold) println(test); My error is: Driver.scala:35: error: type mismatch; found : Unit required: scala.collection.mutable.ArrayBuffer[String] ho = stringParse(str, 0, ho, 0); ^one error found When I add an equals sign after the arguments in the method declaration, like so: def stringParse ( exp: String, pos: Int, expreshHolder: ArrayBuffer[String], follow: Int ) ={....} It changes it to "Any". I am confused on how this works. Any ideas? Much appreciated.

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• Cleaning up when exiting an OpenGL app

  - by Daniel

  This might be a dumb question but I've spent some time asking Google and haven't been able to find anything. I have an an OSX OpenGL app I'm trying to modify. When I create the app a whole bunch of initialisation functions are called -- including methods where I can specify my own mouse and keyboard handlers etc. For example: glutInit(&argc, argv); glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA); glutInitWindowPosition(100, 100); glutInitWindowSize(700, 700); glutCreateWindow("Map Abstraction"); glutReshapeFunc(resizeWindow); glutDisplayFunc(renderScene); glutIdleFunc(renderScene); glutMouseFunc(mousePressedButton); glutMotionFunc(mouseMovedButton); glutKeyboardFunc(keyPressed); At some point I pass control to glutMainLoop and my application runs. In the process of running I create a whole bunch of objects. I'd like to clean these up. Is there any way I can tell GLUT to call a cleanup method before it quits?

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• Java - Reading a csv file line by line - stuck with weird non-existent characters being read!

  - by rockit

  hello fellow java developers. I'm having a very strange issue. I'm trying to read a csv file line by line. Im at the point where Im just testing out the reading of the lines. ONly each time that I read a line, the line contains square characters between each character of text. I even saved the file as a txt file in wordpad and notepad with no change. Thus I must be doing something stupid... I have a csv file, standard csv file, yes a text file with commas in it. I try to read a line of text, but the text is all f-ed up and cannot find the phrase within the text. Any advice? code below. //open csv File filReadMe = new File(strRoot + "data2.csv"); BufferedReader brReadMe = new BufferedReader(new InputStreamReader(new FileInputStream(filReadMe))); String strLine = brReadMe.readLine(); //for all lines while (strLine != null){ //if line contains "(see also" if (strLine.toLowerCase().contains("(see also")){ //write line from "(see also" to ")" int iBegin = strLine.toLowerCase().indexOf("(see also"); String strTemp = strLine.substring(iBegin); int iLittleEnd = strTemp.indexOf(")"); System.out.println(strLine.substring(iBegin, iBegin + iLittleEnd)); } //update line strLine = brReadMe.readLine(); } //end for brReadMe.close();

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• Flex/Actionscript image display problem.

  - by IanH

  I'm trying to extend the Image class but hit a problem that I can't get past. I have a private image (img) that loads an image and a function that takes that image and copies it onto the parent. The debug function "copyit2" displays the image fine (so I know it's loaded OK). But the function "copyit" doesn't work - it just displays a white rectangle. I can't see how to make copyit work so that the original image is copied to the BitmapData and then subsequenty copied onto the parent? (The idea is to do some processing on the Bitmap data before it is displayed, although this isn't shown here to keep the example simple.) I suspect it is something to do with the security of loading images, but I'm loading it from the same server as the application is run from - so this shouldn't be a problem? Thanks for any help anyone can provide. Ian package zoomapackage { import flash.display.Bitmap; import flash.display.BitmapData; import flash.display.Sprite; import flash.events.MouseEvent; import flash.geom.Matrix; import flash.geom.Point; import flash.geom.Rectangle; import flash.net.*; import mx.controls.Image; import mx.events.FlexEvent; public dynamic class Zooma extends Image { private var img:Image; public function copyit():void { var imgObj:BitmapData = new BitmapData(img.content.width, img.content.height, false); imgObj.draw(img); var matrix:Matrix = new Matrix(); this.graphics.beginBitmapFill(imgObj, matrix, false,true); this.graphics.drawRect(0, 0, this.width , this.height); this.graphics.endFill(); } public function copyit2():void { this.source = img.source; } public function Zooma() { super(); img = new Image(); img.load("http://localhost/Koala.jpg"); } } }

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• Regular Expression with Names and Emails

  - by Nina

  I am having a problem with regular expressions at the moment. What I'm trying to do is that for each line through the iteration, it checks for this type of pattern: Lastname, Firstname If it finds the name, then it will take the first letter of the first name, and the first six letters of the lastname and form it as an email. I have the following: $checklast = "[A-z],"; $checkfirst = "[A-z]"; if (ereg($checklast, $parts[1])||ereg($checkfirst, $parts[2])){ $first = preg_replace($checkfirst, $checkfirst{1,1}, $parts[2]); print "<a href='mailto:[email protected];'> $parts[$i] </a>"; } This one obviously broke the code. But I was initially attempting to find only the first letter of the firstname and then after that the first six letters of the lastname followed by the @email.com This didn't work out too well. I'm not sure what to do at this point. Any help is much appreciated.

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• C++ Builder 2010 Exception Dead Lock ???

  - by James

  Hello Is this some kind of exception dead lock i am facing? How to avoid it ? Have a look at below line where i have TIdContext objects of connected clients stored in an objlist and at times i need to process it. But if one user is disconnected while another thread is processing the list, then for that freed TIdContext-Data object I am getting Access voilation, Ok its fine i am using try/catch but problem is that at below line there is some kind of dead lock and process hangs , if i attach a debuger it show Access voilation Again and Again and Again, and cpu coonsumption goes up because of that exception dead lock. AnsiString UserID = ((Tmyobject*) ((TIdContext*) ObjList->Objects[i])->Data)->UserID; i know i can check before accessing the object, if object is not Null, It works.. But my question is what if once in a blue moon the Data object is freed at the point when NULL check is performed and on next line when again i am accessing the object i get same dead lock ??? So how to avoid/handle this dead lock exception ? Here is the call stack... :005F07C0 System::AnsiStringBase::AnsiStringBase(this=:0285FCE0, src=????) :0040223F System::AnsiStringT<0>::AnsiStringT<0>(this=:0285FCE0, src=:00000008) :00457996 TSomeClass::SomeFunction(this=:009D8230, UserID={ }, DataSize={ }, ) :0047BFF1 __linkproc__ ThreadProc(Thread=:009561C0) :004AD00E __linkproc__ ThreadWrapper(Parameter=:009EAA30) :7c80b729 ; C:\WINDOWS\system32\kernel32.dll Please helppppppppppppppppppppp Thanks

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• C programming - How to print numbers with a decimal component using only loops?

  - by californiagrown

  I'm currently taking a basic intro to C programming class, and for our current assignment I am to write a program to convert the number of kilometers to miles using loops--no if-else, switch statements, or any other construct we haven't learned yet are allowed. So basically we can only use loops and some operators. The program will generate three identical tables (starting from 1 kilometer through the input value) for one number input using the while loop for the first set of calculations, the for loop for the second, and the do loop for the third. I've written the entire program, however I'm having a bit of a problem with getting it to recognize an input with a decimal component. Here is what I have for the while loop conversions: #include <stdio.h> #define KM_TO_MILE .62 main (void) { double km, mi, count; printf ("This program converts kilometers to miles.\n"); do { printf ("\nEnter a positive non-zero number"); printf (" of kilometers of the race: "); scanf ("%lf", &km); getchar(); }while (km <= 1); printf ("\n KILOMETERS MILES (while loop)\n"); printf (" ========== =====\n"); count = 1; while (count <= km) { mi = KM_TO_MILE * count; printf ("%8.3lf %14.3lf\n", count, mi); ++count; } getchar(); } The code reads in and converts integers fine, but because the increment only increases by 1 it won't print a number with a decimal component (e.g. 3.2, 22.6, etc.). Can someone point me in the right direction on this? I'd really appreciate any help! :)

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• Self organizing layouts

  - by user613326

  Quite a while ago i was more in websites building then i am now. In my time there where huge debates about what to use; tables or pure CSS alternatives. I went out of the webdesigning, but now an old question re-surfaces. What i would like to create is a web page design that depending on screensize, would self organize the page into columns, so that for example on a PDA it would show 1 column On an old computer monitor, it would show 2 colomns, and on a widescreen laptop it would show 3 columns. I forgot how this was called and how it was done in the past, it had to do with XML and storing data seperate from design (if i remember well), perhaps these days better methods exist to do that, does this, anyone ring this a bell ? Also i note a lot is possible with Jquery and and brouwser depending webkits. But i need to make sure that it would run on all (modern) brouwsers : Iexplorer, Firefox, chrome And Jquery is nice too, but i am kinda woried that some day one of these brouwser vendors decides that jscript like java isnt enabled by default (or is that very unlikely ?)11 Perhaps someone can point me to a method that is the prefered way to do this.

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• How to delete a row from a typed dataset and save it to a database?

  - by Zingam

  I am doing this as a small project to learn about disconnected and connected models in .NET 4.0 and SQL Server 2008 R2. I have three tables: Companies (PK CompanyID) Addresses (PK AddressID, FK CompanyID) ContactPersons (PK ContactPersonID, FK CompanyID) CompanyID is assigned manually by the users. The other IDs are auto-generated. Companies has a one-to-many relationship with ContactPerson. I have set any changes to cascade. I display all records in Companies in a DataGridView and when a row is clicked, the corresponding records in ContactPersons are displayed in a second DataGridView. I have successfully implemented updating and inserting new records but I completely fail in my attempts to delete rows and save the changes to the database. I us a typed dataset. If I use this: DataRow[] contactPersonRows = m_SoldaCompaniesFileDataSet.ContactPersons.Select("ContactPersonID = " + this.m_CurrentContactPerson.ContactPersonID); m_SoldaCompaniesFileDataSet.ContactPersons.Rows.Remove(contactPersonRows[0]); The records are displayed properly in the DataGridView but are not saved in the database later. If I use this: DataRow row = m_SoldaCompaniesFileDataSet.ContactPersons.Rows.Find(this.m_CurrentContactPerson.ContactPersonID); row.Delete(); The records are set but I get an exeception: DeletedRowInaccessibleException, when I try to refresh the DataGridView. The exception pop-s up in the auto-generated dataset.design file. I am pretty much stuck at this point since yesterday. I cannot find anything anywhere that remotely resembles my problem. And I cannot understand actually what is going on.

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• im i doing this right or wrong using pointers in C

  - by Amandeep Singh Dhari

  i like to point out that i need some help with my home work, ok the lectuer gave us the idea of a program and we have to make it from bottom to top. got to have user to type in two set of string. pointers take in the value and then puts into a prototype i need to make a 3rd pointer that has the value of p1 and p2. like this p1 = asd, p2 = qwe and p3 = asdqwe #include "stdafx.h" #include <ctype.h> char *mystrcat(char*s1p, char*s2p); // Prototype char main(void) { char string1[80]; char string2[80]; printf("%s", "enter in your srting one "); gets_s(string1); printf("%s", "enter in your srting two "); gets_s(string2); *mystrcat(string1, string2); return 0; } char *mystrcat(char *s1p,char *s2p) { //char *string3; //char *string4; //string3 = s1p; //string4 = s2p; printf("whatever = %s%s\n", s1p, s2p); return 0; } this is the code that i made so far just need some help, thank guys in advance.

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• Get filename from path

  - by Eric

  I am trying to parse the filename from paths. I have this: my $filepath = "/Users/Eric/Documents/foldername/filename.pdf"; $filepath =~ m/^.*\\(.*[.].*)$/; print "Linux path:"; print $1 . "\n\n"; print "-------\n"; my $filepath = "c:\\Windows\eric\filename.pdf"; $filepath =~ m/^.*\\(.*[.].*)$/; print "Windows path:"; print $1 . "\n\n"; print "-------\n"; my $filepath = "filename.pdf"; $filepath =~ m/^.*\\(.*[.].*)$/; print "Without path:"; print $1 . "\n\n"; print "-------\n"; But that returns: Linux path: ------- Windows path:Windowsic ilename.pdf ------- Without path:Windowsic ilename.pdf ------- I am expecting this: Linux path: filename.pdf ------- Windows path: filename.pdf ------- Without path: filename.pdf ------- Can somebody please point out what I am doing wrong? Thanks! :)

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• DDD: Enum like entities

  - by Chris

  Hi all, I have the following DB model: **Person table** ID | Name | StateId ------------------------------ 1 Joe 1 2 Peter 1 3 John 2 **State table** ID | Desc ------------------------------ 1 Working 2 Vacation and domain model would be (simplified): public class Person { public int Id { get; } public string Name { get; set; } public State State { get; set; } } public class State { private int id; public string Name { get; set; } } The state might be used in the domain logic e.g.: if(person.State == State.Working) // some logic So from my understanding, the State acts like a value object which is used for domain logic checks. But it also needs to be present in the DB model to represent a clean ERM. So state might be extended to: public class State { private int id; public string Name { get; set; } public static State New {get {return new State([hardCodedIdHere?], [hardCodeNameHere?]);}} } But using this approach the name of the state would be hardcoded into the domain. Do you know what I mean? Is there a standard approach for such a thing? From my point of view what I am trying to do is using an object (which is persisted from the ERM design perspective) as a sort of value object within my domain. What do you think? Question update: Probably my question wasn't clear enough. What I need to know is, how I would use an entity (like the State example) that is stored in a database within my domain logic. To avoid things like: if(person.State.Id == State.Working.Id) // some logic or if(person.State.Id == WORKING_ID) // some logic

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• Splitting a set of object into several subsets of 'similar' objects

  - by doublep

  Suppose I have a set of objects, S. There is an algorithm f that, given a set S builds certain data structure D on it: f(S) = D. If S is large and/or contains vastly different objects, D becomes large, to the point of being unusable (i.e. not fitting in allotted memory). To overcome this, I split S into several non-intersecting subsets: S = S1 + S2 + ... + Sn and build Di for each subset. Using n structures is less efficient than using one, but at least this way I can fit into memory constraints. Since size of f(S) grows faster than S itself, combined size of Di is much less than size of D. However, it is still desirable to reduce n, i.e. the number of subsets; or reduce the combined size of Di. For this, I need to split S in such a way that each Si contains "similar" objects, because then f will produce a smaller output structure if input objects are "similar enough" to each other. The problems is that while "similarity" of objects in S and size of f(S) do correlate, there is no way to compute the latter other than just evaluating f(S), and f is not quite fast. Algorithm I have currently is to iteratively add each next object from S into one of Si, so that this results in the least possible (at this stage) increase in combined Di size: for x in S: i = such i that size(f(Si + {x})) - size(f(Si)) is min Si = Si + {x} This gives practically useful results, but certainly pretty far from optimum (i.e. the minimal possible combined size). Also, this is slow. To speed up somewhat, I compute size(f(Si + {x})) - size(f(Si)) only for those i where x is "similar enough" to objects already in Si. Is there any standard approach to such kinds of problems? I know of branch and bounds algorithm family, but it cannot be applied here because it would be prohibitively slow. My guess is that it is simply not possible to compute optimal distribution of S into Si in reasonable time. But is there some common iteratively improving algorithm?

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• How difficult is it for an old-school programmer to pick up an FPGA kit and make something useful wi

  - by JUST MY correct OPINION

  I'm an old, old, old coder. (How old? I've used paper tape in anger.) I've programmed in a lot of languages and under a lot of paradigms (spaghetti, structured, object-oriented, functional and a smattering of logical). I'm getting bored. FPGAs look interesting to me. I have the crazy notion of resurrecting some of the ancient hardware I worked on in the days using FPGAs. I know this can be done because I've seen PDP-10 and PDP-11 implementations in FPGAs. I'd like to do the same for a few machines that are perhaps not as popular as those two, however. While I am an old, old coder, what I am not is an electronics or computer systems engineer. I'll be learning from scratch if I go down this path. My question, therefore, is two-fold: How difficult will it be for this old dinosaur to pick up and learn FPGAs to the point that interesting (not necessarily practical -- more from a hobbyist perspective) projects can be made? What should I start with learning-wise to go down this path? I know where to get FPGA kits, but I haven't found anything like "FPGAs for Complete Dinosaurs" yet anywhere out there.

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• Why doesn't the SplitView iPhone template have a nib file for the RootView?

  - by Dr Dork

  I'm diving into iPad development and am learning a lot quickly, but everywhere I look, I have questions. After creating a new SplitView app in Xcode using the template, it generates the AppDelegate class, RootViewController class, and DetailViewController class. Along with that, it creates a .xib files for MainWinow.xib and DetailView.xib. How do these five files work together? Why is there a nib file for the DetailView, but not the RootView? When I double click on the MainWindow.xib file, Interface Builder launches without a "View" window, why? Below is the code for didFinishLaunchingWithOptions method inside the AppDelegate class. Why are we adding the splitViewController as a subview? (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after app launch rootViewController.managedObjectContext = self.managedObjectContext; // Add the split view controller's view to the window and display. [window addSubview:splitViewController.view]; [window makeKeyAndVisible]; return YES; } Thanks so much in advance for all your help! I still have a lot to learn, so I apologize if this question is absurd in any way. I'm going to continue researching these questions right now!

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• How do I consume a self hosted WCF service with Compact Framework client?

  - by pitprog

  Hello - I've been trying to figure out how to consume a self hosted WCF service from a Windows CE device. I've not found any good resources that walk through this process online. I've found some good samples for self hosting, and that part seems to be working fine, but not sure how to go about consuming on the compact framework. In the past I was able to use NetCFSvcUtil.exe, but this doesn't seem to work with a self hosted service. NetCFSvcutil says: The underlying connection was closed: An unexpected error occurred on a receive. Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. I've used Jason Henderson's sample http://www.codeproject.com/KB/WCF/WCFexample.aspx to get started with self hosting and that part works as expected. Can any one point me to a sample where a compact framework client is used to consume a self hosted WCF service? or give a brief explanation of how I create the plumbing on the compact framework side? For the host application I'm using a WinForm .Net 3.5 project and for the client a WinForm Compact Framework 3.5 project. Thanks!

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