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• Refactoring Singleton Overuse

  - by drharris

  Today I had an epiphany, and it was that I was doing everything wrong. Some history: I inherited a C# application, which was really just a collection of static methods, a completely procedural mess of C# code. I refactored this the best I knew at the time, bringing in lots of post-college OOP knowledge. To make a long story short, many of the entities in code have turned out to be Singletons. Today I realized I needed 3 new classes, which would each follow the same Singleton pattern to match the rest of the software. If I keep tumbling down this slippery slope, eventually every class in my application will be Singleton, which will really be no logically different from the original group of static methods. I need help on rethinking this. I know about Dependency Injection, and that would generally be the strategy to use in breaking the Singleton curse. However, I have a few specific questions related to this refactoring, and all about best practices for doing so. How acceptable is the use of static variables to encapsulate configuration information? I have a brain block on using static, and I think it is due to an early OO class in college where the professor said static was bad. But, should I have to reconfigure the class every time I access it? When accessing hardware, is it ok to leave a static pointer to the addresses and variables needed, or should I continually perform Open() and Close() operations? Right now I have a single method acting as the controller. Specifically, I continually poll several external instruments (via hardware drivers) for data. Should this type of controller be the way to go, or should I spawn separate threads for each instrument at the program's startup? If the latter, how do I make this object oriented? Should I create classes called InstrumentAListener and InstrumentBListener? Or is there some standard way to approach this? Is there a better way to do global configuration? Right now I simply have Configuration.Instance.Foo sprinkled liberally throughout the code. Almost every class uses it, so perhaps keeping it as a Singleton makes sense. Any thoughts? A lot of my classes are things like SerialPortWriter or DataFileWriter, which must sit around waiting for this data to stream in. Since they are active the entire time, how should I arrange these in order to listen for the events generated when data comes in? Any other resources, books, or comments about how to get away from Singletons and other pattern overuse would be helpful.

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• Remote XP -> Win98 WMI Connection

  - by Logan Young

  I've asked this on Technet, but because Win98 is no longer supported, I can't get any decent information, I was hoping there might be some "old school" developers here who might be able to help me. There is an application that we use a lot at work. This application should run 8am-5pm with as little interruption as possible. Most of the computers where this application runs are using Win98, and we have no way to upgrade them because we can't buy new hardware at the moment. My computer is running WinXP, so I thought of a way to make sure that this application runs all the time: The idea I had was to develop a Windows Service that executes a VBScript file that contains a WMI query to get a list of processes from each computer. Each list is then examined, and, depending on whether or not the target application is running, it will either do nothing, or it will execute another VBScript file that contains a WMI query that will be used to start the target application remotely. I later found a way to do this all with 1 VBScript file (see code below) My problem is in the remote connection to the target computers. I've installed WMI Core 1.5 on them, but every time I try the remote connection, I get the following: The remote server is unavailable or does not exist: 'GetObject' VBScript runtime error 800A01CE I've done some research, and all I've found is info about DCOM Config and Windows Firewall, but Win98 doesn't have either of these. ' #### Variables and constants #### Const HIDDEN_WINDOW = 12 Dim T ' #### End Variables and constants #### Main() Sub Main() ' #### Get Process information from WMI Computer = "." Set WMI = GetObject("winmgmts:" & _ "{ImpersonationLevel=Impersonate}!\\" & Computer & "\root\cimv2") Set Settings = WMI.ExecQuery("SELECT * FROM Win32_Process") For Each Process In Settings ' #### If the application is found to be running, set a value to indicate this If Process.Name = "NOTEPAD.EXE" Then T = True End If Next ' #### T will only have a value if the application is not running. We therefore ' #### evaluate it to determine if it has a value or not. If not, start the application If Not T Then 'MsgBox("Application not found.") Set Startup = WMI.Get("Win32_ProcessStartup") Set Config = Startup.SpawnInstance_ Config.ShowWindow = HIDDEN_WINDOW Set Process = GetObject("winmgmts:root\cimv2:Win32_Process") errReturn = Process.Create(_ "C:\Windows\notepad.exe", null, Config, intProcessID) End If End Sub This uses WMI to get the list of processes from the local computer and, if the target application is running, it'll do nothing, otherwise it'll forcefully start the target application. The problem is that this works only if I specify the local comuter, if I target another computer, I get the error mentioned above. Does anyone have any ideas? Thanks in advance for the help!

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• Linked lists in Java - help with assignment

  - by user368241

  Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. Here is my try to write the method indexOf (int ch). Kindly assist me with fixing the bugs so I can move on. public int indexOf (int ch) { int count = 0; charNode pose = _head; if (pose == null ) { return -1; } for (pose = _head; pose!=null && pose.getNext()!='ch'; pose = pose.getNext()) { count++; } if (pose!=null) return count; else return -1; }

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• Is there a way to keep track of the ordering of items in a dictionary?

  - by Corpsekicker

  I have a Dictionary<Guid, ElementViewModel>. (ElementViewModel is our own complex type.) I add items to the dictionary with a stock standard items.Add(Guid.NewGuid, new ElementViewModel() { /*setters go here*/ });, At a later stage I remove some or all of these items. A simplistic view of my ElementViewModel is this: class ElementViewModel { Guid Id { get; set; } string Name { get; set; } int SequenceNo { get; set; } } It may be significant to mention that the SequenceNos are compacted within the collection after adding, in case other operations like moving and copying took place. {1, 5, 6} - {1, 2, 3} A simplistic view of my remove operation is: public void RemoveElementViewModel(IEnumerable<ElementViewModel> elementsToDelete) { foreach (var elementViewModel in elementsToDelete) items.Remove(elementViewModel.Id); CompactSequenceNumbers(); } I will illustrate the problem with an example: I add 3 items to the dictionary: var newGuid = Guid.NewGuid(); items.Add(newGuid, new MineLayoutElementViewModel { Id = newGuid, SequenceNo = 1, Name = "Element 1" }); newGuid = Guid.NewGuid(); items.Add(newGuid, new MineLayoutElementViewModel { Id = newGuid, SequenceNo = 2, Name = "Element 2" }); newGuid = Guid.NewGuid(); items.Add(newGuid, new MineLayoutElementViewModel { Id = newGuid, SequenceNo = 3, Name = "Element 3" }); I remove 2 items RemoveElementViewModel(new List<ElementViewModel> { item2, item3 }); //imagine I had them cached somewhere. Now I want to add 2 other items: newGuid = Guid.NewGuid(); items.Add(newGuid, new MineLayoutElementViewModel { Id = newGuid, SequenceNo = 2, Name = "Element 2, Part 2" }); newGuid = Guid.NewGuid(); items.Add(newGuid, new MineLayoutElementViewModel { Id = newGuid, SequenceNo = 3, Name = "Element 3, Part 2" }); On evaluation of the dictionary at this point, I expected the order of items to be "Element 1", "Element 2, Part 2", "Element 3, Part 2" but it is actually in the following order: "Element 1", "Element 3, Part 2", "Element 2, Part 2" I rely on the order of these items to be a certain way. Why is it not as expected and what can I do about it?

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• Primary language - QtC++, C#, Java?

  - by Airjoe

  I'm looking for some input, but let me start with a bit of background (for tl;dr skip to end). I'm an IT major with a concentration in networking. While I'm not a CS major nor do I want to program as a vocation, I do consider myself a programmer and do pretty well with the concepts involved. I've been programming since about 6th grade, started out with a proprietary game creation language that made my transition into C++ at college pretty easy. I like to make programs for myself and friends, and have been paid to program for local businesses. A bit about that- I wrote some programs for a couple local businesses in my senior year in high school. I wrote management systems for local shops (inventory, phone/pos orders, timeclock, customer info, and more stuff I can't remember). It definitely turned out to be over my head, as I had never had any formal programming education. It was a great learning experience, but damn was it crappy code. Oh yeah, by the way, it was all vb6. So, I've used vb6 pretty extensively, I've used c++ in my classes (intro to programming up to algorithms), used Java a little bit in another class (had to write a ping client program, pretty easy) and used Java for some simple Project Euler problems to help learn syntax and such when writing the program for the class. I've also used C# a bit for my own simple personal projects (simple programs, one which would just generate an HTTP request on a list of websites and notify if one responded unexpectedly or not at all, and another which just held a list of things to do and periodically reminded me to do them), things I would've written in vb6 a year or two ago. I've just started using Qt C++ for some undergrad research I'm working on. Now I've had some formal education, I [think I] understand organization in programming a lot better (I didn't even use classes in my vb6 programs where I really should have), how it's important to structure code, split into functions where appropriate, document properly, efficiency both in memory and speed, dynamic and modular programming etc. I was looking for some input on which language to pick up as my "primary". As I'm not a "real programmer", it will be mostly hobby projects, but will include some 'real' projects I'm sure. From my perspective: QtC++ and Java are cross platform, which is cool. Java and C# run in a virtual machine, but I'm not sure if that's a big deal (something extra to distribute, possibly a bit slower? I think Qt would require additional distributables too, right?). I don't really know too much more than this, so I appreciate any help, thanks! TL;DR Am an avocational programmer looking for a language, want quick and straight forward development, liked vb6, will be working with database driven GUI apps- should I go with QtC++, Java, C#, or perhaps something else?

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• Create a Counter within a For-Loop?

  - by Todd Hartman

  I am a novice programmer and apologize upfront for the complicated question. I am trying to create a lexical decision task for experimental research, in which respondents must decide if a series of letters presented on the screen make a "word" or "not a word". Everything works reasonably well except for the bit where I want to randomly select a word (category A) or nonword (category B) for each of 80 trials from a separate input file (input.txt). The randomization works, but some elements from each list (category A or B) are skipped because I have used "round.catIndex = j;" where "j" is a loop for each successive trial. Because some trials randomly select from Category A and other from Category B, "j" does not move successively down the list for each category. Instead, elements from the Category A list may be selected from something like 1, 2, 5, 8, 9, 10, and so on (it varies each time because of the randomization). To make a long story short(!), how do I create a counter that will work within the for-loop for each trial, so that every word and nonword from Category A and B, respectively, will be used for the lexical decision task? Everything I have tried thus far does not work properly or breaks the javascript entirely. Below is my code snippet and the full code is available at http://50.17.194.59/LDT/trunk/LDT.js. Also, the full lexical decision task can be accessed at http://50.17.194.59/LDT/trunk/LDT.php. Thanks! function initRounds() { numlst = []; for (var k = 0; k<numrounds; k++) { if (k % 2 == 0) numlst[k] = 0; else numlst[k] = 1; } numlst.sort(function() {return 0.5 - Math.random()}) for (var j = 0; j<numrounds; j++) { var round = new LDTround(); if (numlst[j] == 0) { round.category = input.catA.datalabel; } else if (numlst[j] == 1) { round.category = input.catB.datalabel; } // pick a category & stimulus if (round.category == input.catA.datalabel) { round.itemtype = input.catA.itemtype; round.correct = 1; round.catIndex = j; } else if (round.category == input.catB.datalabel) { round.itemtype = input.catB.itemtype; round.correct = 2; round.catIndex = j; } roundArray[i].push(round); } return roundArray; }

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• When can Java produce a NaN (with specific code question)

  - by Brent

  I'm a bit perplexed by some code I'm currently writing. I am trying to preform a specific gradient descent (main loop included below) and depending on the initial conditions I will alternatively get good looking results (perhaps 20% of the time) or everything becomes NaN (the other 80% of the time). However it seems to me that none of the operations in my code could produce NaN's when given honest numbers! My main loop is: // calculate errors delta = m1 + m2 - M; eta = f1 + f2 - F; for (int i = 0; i < numChildren; i++) { epsilon[i] = p[i]*m1+(1-p[i])*m2+q[i]*f1+(1-q[i])*f2-C[i]; } // use errors in gradient descent // set aside differences for the p's and q's float mDiff = m1 - m2; float fDiff = f1 - f2; // first update m's and f's m1 -= rate*delta; m2 -= rate*delta; f1 -= rate*eta; f2 -= rate*eta; for (int i = 0; i < numChildren; i++) { m1 -= rate*epsilon[i]*p[i]; m2 -= rate*epsilon[i]*(1-p[i]); f1 -= rate*epsilon[i]*q[i]; f2 -= rate*epsilon[i]*(1-q[i]); } // now update the p's and q's for (int i = 0; i < numChildren; i++) { p[i] -= rate*epsilon[i]*mDiff; q[i] -= rate*epsilon[i]*fDiff; } This behavior can be seen when we have rate = 0.01; M = 30; F = 30; C = {15, 25, 35, 45}; with the p[i] and q[i] chosen randomly uniformly between 0 and 1, m1 and m2 chosen randomly uniformly to add to M, and f1 and f2 chosen randomly uniformly to add up to F. Does anyone see anything that could create these NaN's?

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• Why jQuery selector can't work but getElementById works in this scenario?

  - by Stallman

  Here is the HTML: <html> <head> <script type="text/javascript" src="jquery-1.7.2.min.js"></script> <script type="text/javascript" charset="utf-8" src="jquery-1.7.2.js"></script> <script type="text/javascript" src="access.js"></script> </head> <body> <button id="trigger"></button> <img id= "testElement" style= "position: absolute; border-color: white; top:340px; left:615px;" width="34px" height= "34px" /> </body> </html> And the access.js file is: $(document).ready( function(){ $('#trigger').click(function(){ $('#testElement').src="success.png"; //THIS WON'T WORK. document.getElementById('testElement').src= "success.png"; //BUT THIS WORKS. }); }); I know that if I use $, the return object is a jQuery object. It's not the same as getElementById. But why the jQuery selector can't work here? I need the jQuery object to make more operations like "append/style"... Thanks. UPDATE Too much correct answers appear at almost the same time... Please give more explanations to let me decide who I should give the credit, thanks!!! Sorry for my poor understanding of your correct answer... I just want more detail. Are all the attribute nodes(src/width/height...) not the property of jQuery object? So does the jQuery selector only select DOM Element Node like ? Thank you! 3. List item

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• SQL Cartesian product joining table to itself and inserting into existing table

  - by Emma

  I am working in phpMyadmin using SQL. I want to take the primary key (EntryID) from TableA and create a cartesian product (if I am using the term correctly) in TableB (empty table already created) for all entries which share the same value for FieldB in TableA, except where TableA.EntryID equals TableA.EntryID So, for example, if the values in TableA were: TableA.EntryID TableA.FieldB 1 23 2 23 3 23 4 25 5 25 6 25 The result in TableB would be: Primary key EntryID1 EntryID2 FieldD (Default or manually entered) 1 1 2 Default value 2 1 3 Default value 3 2 1 Default value 4 2 3 Default value 5 3 1 Default value 6 3 2 Default value 7 4 5 Default value 8 4 6 Default value 9 5 4 Default value 10 5 6 Default value 11 6 4 Default value 12 6 5 Default value I am used to working in Access and this is the first query I have attempted in SQL. I started trying to work out the query and got this far. I know it's not right yet, as I’m still trying to get used to the syntax and pieced this together from various articles I found online. In particular, I wasn’t sure where the INSERT INTO text went (to create what would be an Append Query in Access). SELECT EntryID FROM TableA.EntryID TableA.EntryID WHERE TableA.FieldB=TableA.FieldB TableA.EntryID<>TableA.EntryID INSERT INTO TableB.EntryID1 TableB.EntryID2 After I've got that query right, I need to do a TRIGGER query (I think), so if an entry changes it's value in TableA.FieldB (changing it’s membership of that grouping to another grouping), the cartesian product will be re-run on THAT entry, unless TableB.FieldD = valueA or valueB (manually entered values). I have been using the Designer Tab. Does there have to be a relationship link between TableA and TableB. If so, would it be two links from the EntryID Primary Key in TableA, one to each EntryID in TableB? I assume this would not work because they are numbered EntryID1 and EntryID2 and the name needs to be the same to set up a relationship? If you can offer any suggestions, I would be very grateful. Research: http://www.fluffycat.com/SQL/Cartesian-Joins/ Cartesian Join example two Q: You said you can have a Cartesian join by joining a table to itself. Show that! Select * From Film_Table T1, Film_Table T2;

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• Big Oh Notation - formal definition.

  - by aloh

  I'm reading a textbook right now for my Java III class. We're reading about Big-Oh and I'm a little confused by its formal definition. Formal Definition: "A function f(n) is of order at most g(n) - that is, f(n) = O(g(n)) - if a positive real number c and positive integer N exist such that f(n) <= c g(n) for all n = N. That is, c g(n) is an upper bound on f(n) when n is sufficiently large." Ok, that makes sense. But hold on, keep reading...the book gave me this example: "In segment 9.14, we said that an algorithm that uses 5n + 3 operations is O(n). We now can show that 5n + 3 = O(n) by using the formal definition of Big Oh. When n = 3, 5n + 3 <= 5n + n = 6n. Thus, if we let f(n) = 5n + 3, g(n) = n, c = 6, N = 3, we have shown that f(n) <= 6 g(n) for n = 3, or 5n + 3 = O(n). That is, if an algorithm requires time directly proportional to 5n + 3, it is O(n)." Ok, this kind of makes sense to me. They're saying that if n = 3 or greater, 5n + 3 takes less time than if n was less than 3 - thus 5n + n = 6n - right? Makes sense, since if n was 2, 5n + 3 = 13 while 6n = 12 but when n is 3 or greater 5n + 3 will always be less than or equal to 6n. Here's where I get confused. They give me another example: Example 2: "Let's show that 4n^2 + 50n - 10 = O(n^2). It is easy to see that: 4n^2 + 50n - 10 <= 4n^2 + 50n for any n. Since 50n <= 50n^2 for n = 50, 4n^2 + 50n - 10 <= 4n^2 + 50n^2 = 54n^2 for n = 50. Thus, with c = 54 and N = 50, we have shown that 4n^2 + 50n - 10 = O(n^2)." This statement doesn't make sense: 50n <= 50n^2 for n = 50. Isn't any n going to make the 50n less than 50n^2? Not just greater than or equal to 50? Why did they even mention that 50n <= 50n^2? What does that have to do with the problem? Also, 4n^2 + 50n - 10 <= 4n^2 + 50n^2 = 54n^2 for n = 50 is going to be true no matter what n is. And how in the world does picking numbers show that f(n) = O(g(n))? Please help me understand! :(

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• Finding good heuristic for A* search

  - by Martin

  I'm trying to find the optimal solution for a little puzzle game called Twiddle (an applet with the game can be found here). The game has a 3x3 matrix with the number from 1 to 9. The goal is to bring the numbers in the correct order using the minimum amount of moves. In each move you can rotate a 2x2 square either clockwise or counterclockwise. I.e. if you have this state 6 3 9 8 7 5 1 2 4 and you rotate the upper left 2x2 square clockwise you get 8 6 9 7 3 5 1 2 4 I'm using a A* search to find the optimal solution. My f() is simply the number of rotations need. My heuristic function already leads to the optimal solution but I don't think it's the best one you can find. My current heuristic takes each corner, looks at the number at the corner and calculates the manhatten distance to the position this number will have in the solved state (which gives me the number of rotation needed to bring the number to this postion) and sums all these values. I.e. You take the above example: 6 3 9 8 7 5 1 2 4 and this end state 1 2 3 4 5 6 7 8 9 then the heuristic does the following 6 is currently at index 0 and should by at index 5: 3 rotations needed 9 is currently at index 2 and should by at index 8: 2 rotations needed 1 is currently at index 6 and should by at index 0: 2 rotations needed 4 is currently at index 8 and should by at index 3: 3 rotations needed h = 3 + 2 + 2 + 3 = 10 But there is the problem, that you rotate 4 elements at once. So there a rare cases where you can do two (ore more) of theses estimated rotations in one move. This means theses heuristic overestimates the distance to the solution. My current workaround is, to simply excluded one of the corners from the calculation which solves this problem at least for my test-cases. I've done no research if really solves the problem or if this heuristic still overestimates in same edge-cases. So my question is: What is the best heuristic you can come up with? (Disclaimer: This is for a university project, so this is a bit of homework. But I'm free to use any resource if can come up with, so it's okay to ask you guys. Also I will credit Stackoverflow for helping me ;) )

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• Correct use of a "for...in" loop in javascript?

  - by jnkrois

  Hello everybody, before I ask my question I wanted to let everybody know that I appreciate the fact that there's always somebody out there willing to help, and on my end I'll try to give back to the community as much as I can. Thanks Now, I would like to get some pointers as to how to properly take advantage of the "for...in" loop in JavaScript, I already did some research and tried a couple things but it is still not clear to me how to properly use it. Let's say I have a random number of "select" tags in an HTML form, and I don't require the user to select an option for all of them, they can leave some untouched if they want. However I need to know if they selected none or at least one. The way I'm trying to find out if the user selected any of them is by using the "for...in" loop. For example: var allSelected = $("select option:selected"); var totalSelected = $("select option:selected").length; The first variable produces an array of all the selected options. The second variable tells me how many selected options I have in the form (select tags could be more than one and it changes every time). Now, in order to see if any has been selected I loop through each element (selected option), and retrieve the "value" attribute. The default "option" tag has a value="0", so if any selected option returns a value greater than 0, I know at least one option has been selected, however it does not have to be in order, this is my loop so far: for(var i = 0; i < totalSelected; i++){ var eachOption = $(allSelected[i]).val(); var defaultValue = 0; if(eachOption == defaultValue){ ...redirect to another page }else if(eachOption > defaultValue){ ... I display an alert } } My problem here is that as soon as the "if" matches a 0 value, it sends the user to the next page without testing the rest of the elements in the array, and the user could have selected the second or third options. What I really want to do is check all the elements in the array and then take the next action, in my mind this is how I could do it, but I'm not getting it right: var randomValue = 25; for(randomValue in allSelected){ var found = true; var notFound = false if(found){ display an alert }else{ redirect to next page } } This loop or the logic I'm using are flawed (I'm pretty sure), what I want to do is test all the elements in the array against a single variable and take the next action accordingly. I hope this makes some sense to you guys, any help would be appreciated. Thanks, JC

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• PHP problems when transfering code from Windows to OS X

  - by Makka95

  I have recently bought a new MacBook Pro. Before I had my MacBook Pro I was working on a website on my desktop computer. And now I want to transfer this code to my new MacBook Pro. The problem is that when I transfered the code (I put it on Dropbox and simply downloaded it on my MacBook Pro) I started to see lots of error messages in my PHP code. The error message I”m receiving is: Warning: Cannot modify header information - headers already sent by (output started at /some/file.php:1) in /some/file.php on line 23 I have done some research on this and it seems that this error is most frequently caused by a new line, simple whitespace or any output before the <?php sign. I have looked through all the places where I have cookies that are being sent in the HTTP request and also where I'm using the header() function. I haven’t detected any output or whitespace that possibly could interfere and cause this problem. Noteworthy is that the error always says that the output is started at line 1. Which got me thinking if there is some kind of coding differences in the way that the Mac OS X and Windows operating systems handle new lines or white spaces? Or could the Dropbox transfer messed something up? The code on one of the sites(login.php) which produces the error: <?php include "mysql_database.php"; login(); $id = $_SESSION['Loggedin']; setcookie("login", $id, (time()+60*60*24*30)); header('Location: ' . $_SERVER['HTTP_REFERER']); ?> login function: function login() { $connection = connecttodatabase(); $pass = ""; $user = ""; $query = ""; if (isset($_POST['user']) && $_POST['user'] != null) { $user = $_POST['user']; if (isset($_POST['pass']) && $_POST['pass'] != null) { $pass = md5($_POST['pass']); $query = "SELECT ID FROM Anvandare WHERE Nickname='$user' AND Password ='$pass'"; } } if ($query != "") { $id = $connection->query($query); $id = mysqli_fetch_assoc($id); $id = $id['ID']; $_SESSION['Loggedin'] = $id; } closeconnection($connection); } Complete error: Warning: Cannot modify header information - headers already sent by (output started at /Users/name/GitHub/website/login.php:1) in /Users/namn/GitHub/website/login.php on line 9

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• C# ApplicationContext usage

  - by rd42

  Apologies if my terminology is off, I'm new to C#. I'm trying to use an ApplicationContext file to store mysql conn values, like dbname, username, password. The class with mysql conn string is "using" the namespace for the ApplicationContext, but when I print out the connection string, the values are making it. A friend said, "I'm not initializing it" but couldn't stay to expand on what "it" was. and the "Console.WriteLine("1");" in ApplicationContext.cs never shows up. Do I need to create an ApplicationContext object and the call Initialize() on that object? Thanks for any help. ApplicationContext.cs: namespace NewApplication.Context { class ApplicationContext { public static string serverName; public static string username; public static string password; public static void Initialize() { //need to read through config here try { Console.WriteLine("1"); XmlDocument xDoc = new XmlDocument(); xDoc.Load(".\\Settings.xml"); XmlNodeList serverNodeList = xDoc.GetElementsByTagName("DatabaseServer"); XmlNodeList usernameNodeList = xDoc.GetElementsByTagName("UserName"); XmlNodeList passwordNodeList = xDoc.GetElementsByTagName("Password"); } catch (Exception ex) { // MessageBox.Show(ex.ToString()); //TODO: Future write to log file username = "user"; password = "password"; serverName = "localhost"; } } } } MySQLManager.cs: note: dbname is the same as the username as you'll see in the code, I copied this from a friend who does that. using System; using System.Collections.Generic; using System.Linq; using System.Text; using MySql.Data; using MySql.Data.MySqlClient; using NewApplication.Context; namespace NewApplication.DAO { class MySQLManager { private static MySqlConnection conn; public static MySqlConnection getConnection() { if (conn == null || conn.State == System.Data.ConnectionState.Closed) { string connStr = "server=" + ApplicationContext.serverName + ";user=" + ApplicationContext.username + ";database=" + ApplicationContext.username + ";port=3306;password=" + ApplicationContext.password + ";"; conn = new MySqlConnection(connStr); try { Console.WriteLine("Connecting to MySQL... "); Console.WriteLine("Connection string: " + connStr + "\n"); conn.Open(); // Perform databse operations // conn.Close(); } catch (Exception ex) { Console.WriteLine(ex.ToString()); } } return conn; } } } and, thanks for still reading, this is the code that uses the two previous files: class LogDAO { MySqlConnection conn; public LogDAO() { conn = MySQLManager.getConnection(); } Thank you, rd42

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• Hibernate/Spring: getHibernateTemplate().save(...) Freezes/Hangs

  - by ashes999

  I'm using Hibernate and Spring with the DAO pattern (all Hibernate dependencies in a *DAO.java class). I have nine unit tests (JUnit) which create some business objects, save them, and perform operations on them; the objects are in a hash (so I'm reusing the same objects all the time). My JUnit setup method calls my DAO.deleteAllObjects() method which calls getSession().createSQLQuery("DELETE FROM <tablename>").executeUpdate() for my business object table (just one). One of my unit tests (#8/9) freezes. I presumed it was a database deadlock, because the Hibernate log file shows my delete statement last. However, debugging showed that it's simply HibernateTemplate.save(someObject) that's freezing. (Eclipse shows that it's freezing on HibernateTemplate.save(Object), line 694.) Also interesting to note is that running this test by itself (not in the suite of 9 tests) doesn't cause any problems. How on earth do I troubleshoot and fix this? Also, I'm using @Entity annotations, if that matters. Edit: I removed reuse of my business objects (use unique objects in every method) -- didn't make a difference (still freezes). Edit: This started trickling into other tests, too (can't run more than one test class without getting something freezing) Transaction configuration: <bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="dataSource" /> </bean> <tx:advice id="txAdvice" transaction-manager="txManager"> <!-- the transactional semantics... --> <tx:attributes> <!-- all methods starting with 'get' are read-only --> <tx:method name="get*" read-only="true" /> <tx:method name="find*" read-only="true" /> <!-- other methods use the default transaction settings (see below) --> <tx:method name="*" /> </tx:attributes> </tx:advice> <!-- my bean which is exhibiting the hanging behavior --> <aop:config> <aop:pointcut id="beanNameHere" expression="execution(* com.blah.blah.IMyDAO.*(..))" /> <aop:advisor advice-ref="txAdvice" pointcut-ref="beanNameHere" /> </aop:config>

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• Codeigniter: Retrieving data on button click with Ajax

  - by OllyTenerife

  I have a simple webpage which generates a random quote from my database upon refreshing the page. I wish to implement some AJAX and JQuery in order to generate quotes via the button rather than having to refresh the page. I have done some research but I am not sure how to implement this in Codeigniter. My current code is below... Page controller: public function index() { $this->load->model('quote_model', '', TRUE); $data['quotes'] = $this->quote_model->getRandom(); $this->load->view('home', $data); } The view: <?php include ('layout/header.php'); ?> <div class="container-fluid"> <div class="row"> <div class="col-md-4 quote-holder"> <img src="application/assets/alan1.jpg" alt="..." class="img-circle img-responsive"> <br> <blockquote class="text-center"> <p><?php echo $quotes[0]['quote']; ?></p> <footer class="text-center"><?php echo $quotes[0]['character_name']; ?> in <cite title="Source Title"><?php echo $quotes[0]['series_name']; ?></cite></footer> </blockquote> <button type="button" class="btn btn-default center-block">Generate quote</button> </div> </div> <?php include ('layout/footer.php'); ?> Here is the function in the model I am retrieving the data from: function getRandom() { $query = $this->db->query(" SELECT * FROM quotes, characters, series WHERE quotes.series_id = series.series_id AND quotes.character_id = characters.character_id ORDER BY rand() LIMIT 1 "); return $query->result_array(); } Should I simply be using something like this? $("button").click(function(){ $.get( "Page/index", function( data ) { //output data to page element... } });

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• My store returns no code id and breaks 404 error. Magento

  - by numerical25

  I know what the issue is but I dont know how to fix it. I just migrated my magento store locally and I guess possibly some data may have been lost when transferring the DB. the DB is very large. Anyhow, when I login to my admin page, I get a 404 error, page was not found. I debugged the issue and got down to the wire. The exception is thrown in Mage/Core/Model/App.php. Line 759 to be exacted. The following is a snippet. Mage/Core/Model/App.php if (empty($this->_stores[$id])) { $store = Mage::getModel('core/store'); /* @var $store Mage_Core_Model_Store */ if (is_numeric($id)) { $store->load($id); // THIS ID IS FROM Mage_Core_Model_App::ADMIN_STORE_ID and its empty which causes the error } elseif (is_string($id)) { $store->load($id, 'code'); } if (!$store->getCode()) { // RETURNS FALSE HERE BECAUSE NO ID Specified $this->throwStoreException(); } $this->_stores[$store->getStoreId()] = $store; $this->_stores[$store->getCode()] = $store; } The store returns null because $id is null so it therefore does not load any model which explains why it returns false when calling getCode() [EDIT] If you want clarification, please ask for more before voting my post down. Remember I am still trying to get help not get neglected. I am using Version 1.4.1.1. When I type in the URL for admin, I get a 404 page. I walked through the code thouroughly and found that the Model MAGE_CORE_MODEL_STORE::getCode(); Returns Null which triggers the exception. and ends the script. I do not have any other detail. I further troubleshooted the issue by checking the database and that is what the screen shot is. Showing that there is infact data in the Code Colunn. So my question is why is the Model returning a empty column when the column clearly has a value. What can I do to further troubleshoot and figure out why its not working [EDIT UPDATE NEW] I did some research. the reason its returning NULL is because the store ID is null being passed Mage::getStoreConfigFlag('web/secure/use_in_adminhtml', Mage_Core_Model_App::ADMIN_STORE_ID); // THIS IS THE ID being specified Mage_Core_Model_App::ADMIN_STORE_ID has no value in it, so this method throws the exception. Not sure why how to fix this.

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• Android: How to properly exit application when inconsistent condition is unavoidable?

  - by Bevor

  First of all I already read about all this discussion that it isn't a good idea to manually exit an Android application. But in my case it seems to be needed. I have an AsyncTask which does a lof of operations in background. That means downloading data, saving it to local storage and preparing it for usage in application. It could happen that there is no internet connection or something different happens. For all that cases I have an Exception handling which returns the result. And if there is an exception, the application is unusable so I need to exit it. My question is, do I have to do some unregistration unloading or unbinding tasks or something when I exit the application by code or is System.exit(0) ok? I do all this in an AsyncTask, see my example: public class InitializationTask extends AsyncTask<Void, Void, InitializationResult> { private ProcessController processController = new ProcessController(); private ProgressDialog progressDialog; private Activity mainActivity; public InitializationTask(Activity mainActivity) { this.mainActivity = mainActivity; } @Override protected void onPreExecute() { super.onPreExecute(); progressDialog = new ProgressDialog(mainActivity); progressDialog.setMessage("Die Daten werden aufbereitet.\nBitte warten..."); progressDialog.setIndeterminate(true); //means that the "loading amount" is not measured. progressDialog.setCancelable(false); progressDialog.show(); }; @Override protected InitializationResult doInBackground(Void... params) { return processController.initializeData(); } @Override protected void onPostExecute(InitializationResult result) { super.onPostExecute(result); progressDialog.dismiss(); if (!result.isValid()) { AlertDialog.Builder dialog = new AlertDialog.Builder(mainActivity); dialog.setTitle("Initialisierungsfehler"); dialog.setMessage(result.getReason()); dialog.setPositiveButton("Ok", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.cancel(); //TODO cancel application System.exit(0); } }); dialog.show(); } } }

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• How to give properties to c++ classes (interfaces)

  - by caas

  Hello, I have built several classes (A, B, C...) which perform operations on the same BaseClass. Example: struct BaseClass { int method1(); int method2(); int method3(); } struct A { int methodA(BaseClass& bc) { return bc.method1(); } } struct B { int methodB(BaseClass& bc) { return bc.method2()+bc.method1(); } } struct C { int methodC(BaseClass& bc) { return bc.method3()+bc.method2(); } } But as you can see, each class A, B, C... only uses a subset of the available methods of the BaseClass and I'd like to split the BaseClass into several chunks such that it is clear what it used and what is not. For example a solution could be to use multiple inheritance: // A uses only method1() struct InterfaceA { virtual int method1() = 0; } struct A { int methodA(InterfaceA&); } // B uses method1() and method2() struct InterfaceB { virtual int method1() = 0; virtual int method2() = 0; } struct B { int methodB(InterfaceB&); } // C uses method2() and method3() struct InterfaceC { virtual int method2() = 0; virtual int method3() = 0; } struct C { int methodC(InterfaceC&); } The problem is that each time I add a new type of operation, I need to change the implementation of BaseClass. For example: // D uses method1() and method3() struct InterfaceD { virtual int method1() = 0; virtual int method3() = 0; } struct D { int methodD(InterfaceD&); } struct BaseClass : public A, B, C // here I need to add class D { ... } Do you know a clean way I can do this? Thanks for your help edit: I forgot to mention that it can also be done with templates. But I don't like this solution either because the required interface does not appear explicitly in the code. You have to try to compile the code to verify that all required methods are implemented correctly. Plus, it would require to instantiate different versions of the classes (one for each BaseClass type template parameter) and this is not always possible nor desired.

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• jquery mouseent/leave to make div appears

  - by Blake

  I am looking to hover over my list item and have an effect similar to something like facebook chat is my best example..I am able to get the first div to appear but I believe this may be a selector issue because I cant get the rest working properly html <ul id="menu_seo" class="menu"> <li id="menu-seo"><span class="arrowout1"></span>SEO</li> <li id="menu-siteaudits"><span class="arrowout2"></span>Site Audits </li> <li id="menu-linkbuilding"><span class="arrowout3"></span>Link-Building</li> <li id="menu-localseo"><span class="arrowout4"></span>Local SEO</li> </ul> <div id="main_content"> <div id="menu-seo-desc"> <p>SEO management begins with a full website diagnosis of current web strategy Adjustments are made to improve your site’s ability to rank higher on search engines and draw more traffic </p> </div> <div id="menu-seo-desc2"> <p>Usability & site architecture review, Search Engine accessibility and indexing, Keyword research & targeting and Conversion rate optimization </p> </div> </div> css #menu-seo-desc { height:125px; width:210px; background-color:red; border-color:#CCC #E8E8E8 #E8E8E8 #CCC; border-style:solid; border-width:1.5px; border-radius:5px; box-shadow: 1px 0 2px 0px #888; -moz-box-shadow: 1px 0 2px 0px #888; -webkit-box-shadow: 1px 0 2px 1px #888; position:absolute; top:220px; left:350px; display:none; } js <script> $(document).ready(function(){ <script> $(document).ready(function(){ $('#menu_seo').on('#menu-seo', { 'mouseenter': function() { $('#menu-seo-desc').fadeIn(600); $('#menu-seo-desc2').fadeIn(600); }, 'mouseleave': function() { $('#menu-seo-desc').fadeOut(300); $('#menu-seo-desc2').fadeOut(300); } }); }); </script> });

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• Split a binary file into chunks c++

  - by L4nce0

  I've been bashing my head against trying to first divide up a file into chunks, for the purpose of sending over sockets. I can read / write a file easily without splitting it into chunks. The code below runs, works, kinda. It will write a textfile and has a garbage character. Which if this was just for txt, no problem. Jpegs aren't working with said garbage. Been at it for a few days, so I've done my research, and it's time to get some help. I do want to stick strictly to binary readers, as this need to handle any file. I've seen a lot of slick examples out there. (none of them worked for me with jpgs) Mostly something along the lines of while(file)... I subscribe to the, if you know the size, use a for-loop, not a while-loop camp. Thank you for the help!! vector<char*> readFile(const char* fn){ vector<char*> v; ifstream::pos_type size; char * memblock; ifstream file; file.open(fn,ios::in|ios::binary|ios::ate); if (file.is_open()) { size = fileS(fn); file.seekg (0, ios::beg); int bs = size/3; // arbitrary. Actual program will use the socket send size int ws = 0; int i = 0; for(i = 0; i < size; i+=bs){ if(i+bs > size) ws = size%bs; else ws = bs; memblock = new char [ws]; file.read (memblock, ws); v.push_back(memblock); } } else{ exit(-4); } return v; } int main(int argc, char **argv) { vector<char*> v = readFile("foo.txt"); ofstream myFile ("bar.txt", ios::out | ios::binary); for(vector<char*>::iterator it = v.begin(); it!=v.end(); ++it ){ myFile.write(*it,strlen(*it)); } }

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• Why is the page still caching even after the no-cache headers have been sent?

  - by Matthew Grasinger

  I've done a ton of research on this and have asked many people with help and still no success. Here are the details... I'm involved in developing a website that pulls data from various data files, combines them in a temp .csv file, and then is graphed using a popular graphing library: dygraphs. The bulk of the website is written in PHP. The parameters that determine the data that is graphed are stored in the users session, the .csv is named after the users session and available for download, and then the .csv file is written in a script that passes it to the dygraphs object. And we've found, even with the no-cache headers sent: header("Cache-Control: no-cache, must-revalidate"); header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); Many users experience in the middle of a session, (if enough different graphs are generated) the page displaying an older, static rendering of the page (data they had graphed earlier in the session) as if it were cached and loaded instead of getting a new request. It only gets weirder though: I've checked using developer tools in both Firefox and Chrome and both browsers are receiving the no-cache headers just fine; Even when the problem occurs if you view the page source, the source is the correct content (a table/legend is also dynamically created using php, the source shows the correct table, but what is rendered is older content); the page begins to render correctly until the graph is about to be display, and then shows the older content; the older content displays as if it were a completely static overlay--the cached graph does not have the same dynamic features (roll over data point display, zoom and pan, etc.) And it is as if the correct page were somewhere beneath it (the download button for the csv file moves depending on how large the table is. The older, static page does nothing if you click the download .csv button, but if you can manage to find the one in the page beneath it you can click and still download the .csv. The data in the .csv is correct) It is one of the strangest things I've seen in development thus far. Some other relevant facts are that all the problems I've personally experience occurred while I was using Chrome. Non of these symptoms have been reported by Firefox users. IE users have had the same problems (IE users are forced to use chrome frame). I'm at my wits end at this point. We've sent the php headers; we've tried setting the cache profile for php on IIS as "DisableCache" (or whatever); we've tried sending a random query string to the results page; we've tried all the appropriate meta tags--all with no success.

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• CUDA memory transfer issue

  - by Vaibhav Sundriyal

  I am trying to execute a code which first transfers data from CPU to GPU memory and vice-versa. In spite of increasing the volume of data, the data transfer time remains the same as if no data transfer is actually taking place. I am posting the code. #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ #include <sys/time.h> __global__ void device_volume(float *x_d,float *y_d) { int index = blockIdx.x * blockDim.x + threadIdx.x; } int main(void) { float *x_h,*y_h,*x_d,*y_d,*z_h,*z_d; long long size=9999999; long long nbytes=size*sizeof(float); timeval t1,t2; double et; x_h=(float*)malloc(nbytes); y_h=(float*)malloc(nbytes); z_h=(float*)malloc(nbytes); cudaMalloc((void **)&x_d,size*sizeof(float)); cudaMalloc((void **)&y_d,size*sizeof(float)); cudaMalloc((void **)&z_d,size*sizeof(float)); gettimeofday(&t1,NULL); cudaMemcpy(x_d, x_h, nbytes, cudaMemcpyHostToDevice); cudaMemcpy(y_d, y_h, nbytes, cudaMemcpyHostToDevice); cudaMemcpy(z_d, z_h, nbytes, cudaMemcpyHostToDevice); gettimeofday(&t2,NULL); et = (t2.tv_sec - t1.tv_sec) * 1000.0; // sec to ms et += (t2.tv_usec - t1.tv_usec) / 1000.0; // us to ms printf("\n %ld\t\t%f\t\t",nbytes,et); et=0.0; //printf("%f %d\n",seconds,CLOCKS_PER_SEC); // launch a kernel with a single thread to greet from the device //device_volume<<<1,1>>>(x_d,y_d); gettimeofday(&t1,NULL); cudaMemcpy(x_h, x_d, nbytes, cudaMemcpyDeviceToHost); cudaMemcpy(y_h, y_d, nbytes, cudaMemcpyDeviceToHost); cudaMemcpy(z_h, z_d, nbytes, cudaMemcpyDeviceToHost); gettimeofday(&t2,NULL); et = (t2.tv_sec - t1.tv_sec) * 1000.0; // sec to ms et += (t2.tv_usec - t1.tv_usec) / 1000.0; // us to ms printf("%f\n",et); cudaFree(x_d); cudaFree(y_d); cudaFree(z_d); return 0; } Can anybody help me with this issue? Thanks

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• PHP array performance

  - by dfo

  Hi, this is my first question on Stackoverflow, please bear with me. I'm testing an algorithm for 2d bin packing and I've chosen PHP to mock it up as it's my bread-and-butter language nowadays. As you can see on http://themworks.com/pack_v0.2/oopack.php?ol=1 it works pretty well, but you need to wait around 10-20 seconds for 100 rectangles to pack. For some hard to handle sets it would hit the php's 30s runtime limit. I did some profiling and it shows that most of the time my script goes through different parts of a small 2d array with 0's and 1's in it. It either checks if certain cell equals to 0/1 or sets it to 0/1. It can do such operations million times and each times it takes few microseconds. I guess I could use an array of booleans in a statically typed language and things would be faster. Or even make an array of 1 bit values. I'm thinking of converting the whole thing to some compiled language. Is PHP just not good for it? If I do need to convert it to let's say C++, how good are the automatic converters? My script is just a lot of for loops with basic arrays and objects manipulations. Thank you! Edit. This function gets called more than any other. It reads few properties of a very simple object, and goes through a very small part of a smallish array to check if there's any element not equal to 0. function fits($bin, $file, $x, $y) { $flag = true; $xw = $x + $file->get_width();; $yh = $y + $file->get_height(); for ($i = $x; $i < $xw; $i++) { for ($j = $y; $j < $yh; $j++) { if ($bin[$i][$j] !== 0) { $flag = false; break; } } if (!$flag) break; } return $flag; }

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• progress at work

  - by noopize

  I work in a small department in a very large company. Our department operates largely as a independent unit within the company. Each member of the team has a different role. My role within the team is a operations/admin and no one knew of my skills in programing as I never said anything before about it. I just did my work and in the free time read up on things for my own development Our developer who used to look after our websites has left a few months ago. Now when we require edits to our websites even basic HTML changes we outsource the work. We are getting shafted big time. I could of so said something sooner to highlight my skills in this area but I guess I was just happy to do my own development projects. And one reason was they are using asp.net and I have mainly done things in php. I only hinted before that I have done things but I did not want to reveal them before I had completed anything. I was working on something for myself that the company was also trying to implement something similar(e commerce site). I used open source and they decided to go for a propriety solution. Now I have finished my project and showed it to my boss, their project is still not completed and is quite expensive. He was impressed with what I showed him and suggested I should go for courses to learn asp.net. that I may be able to do the development work for them and there are some big upcoming projects in the future. He said this would be a benefit for me that I should look to be doing a better then role then admin. My employer does have a policy if relevent to the role they may support the costs of courses. Now how do I play this what should I say to my boss. I want to get advise on which MS certified courses would be good for asp.net and how to best approach my boss to see if they will pay all the amount for the course. And how much different will asp.net be from php.

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