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• Understanding c-pointers for rows in 2-dimensional array

  - by utdiscant

  I have the following code: int main() { int n = 3, m = 4, a[n][m], i, j, (* p)[m] = a; for (i = 0; i < n; i++) for (j = 0; j < m; j++) a[i][j] = 1; p++; (*p)[2] = 9; return 0; } I have a hard time understanding what p is here, and the consequences of the operations on p in the end. Can someone give me a brief explanation of what happens. I know c-pointers in their simple settings, but here it get slightly more complicated.

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• xpath: determining if the customer has orders

  - by deostroll

  There is an xml dump of the Northwind database here. Document structure is something like: <NorthWind> <Customers></Customers> <Customers></Customers> . . . <Orders></Orders> <Orders></Orders> . . . </NorthWind> Each Customers tag will hold one customer information. Now while I select all Customers how do I furnish a field such that it indicates whether the customer has orders or not; something like a boolean field

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• how to protect an imported win32 dll into a .net application from memory issues

  - by Eric

  I have a c# application that needs to use a legacy win32 dll. The dll is almost its own app, it has dialogs, operations with hardware, etc. When this dll is imported and used, there are a couple of problems that occur: Dragging a dialog (not a windows system dialog, but one created by the dll) across the managed code app causes the UI to not repaint. Further it generates a system out of memory exception from various ui controls. The performance is incredibly slow. There seems to be no way to unload the dll so the memory never gets cleaned up. When we close our managed app, we get another memory exception. At the moment we import each method call as such: [DllImport("dllname.dll", EntryPoint = "MethodName", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]

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• Is it possible to compute the minimum of three numbers by using two comparisons at the same time?

  - by Milo Hou

  I've been trying to think up of some way that I could do two comparisons at the same time to find the greatest/least of three numbers. Arithmetic operations on them are considered "free" in this case. That is to say, the classical way of finding the greater of two, and then comparing it to the third number isn't valid in this case because one comparison depends on the result of the other. Is it possible to use two comparisons where this isn't the case? I was thinking maybe comparing the differences of the numbers somehow or their products or something, but came up with nothing. Just to reemphasize, two comparisons are still done, just that neither comparison relies on the result of the other comparison. EDIT: what about: boolA = A^2 + B^2 < C^2 boolB = A > B if boolA then max=C else if boolB then max=A else max=B

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• return char1 + char2? Isn't it possible?

  - by pocoa

  I'm trying to return a string from a function. Which basically adds some chars together and return the string representation. string toString() { char c1, c2, c3; // some code here return c1 + c2; // Error: invalid conversion from `char' to `const char*' } it is possible to return boolean values like return c1 == 'x'. Isn't it possible to return string values? I know that it is possible to it like this: string result; result.append(c1, c2); return result; I'm new to C++ so I thought that there must be more elegant solution around.

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• jquery: Toggle elements based on result from a function

  - by Svish

  I have a number of table rows that I would like to toggle the visibility of. They should be visible if a data item I have set on them earlier equals a selected value in a form. This is what I have so far: $('#category-selector').change(function(event) { var category_id = $(this).val(); if(!category_id) { $('tr', '#table tbody').show(); } else { $('tr', '#table tbody').toggle(); } }); Of course this just toggles them on and off. Thing is that I thought I was able to give toggle a function that would decide if each row should be on or off, but it turns out I can only give it a boolean condition which would be an all or nothing deal kind of... So, I have this function: function() { return $(this).data('category_id') == category_id; } How can I use that to go through all the rows and toggle them on or off? Or is there a better approach to this? What should I do?

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• What is the most efficient functional version of the following imperative code?

  - by justin.r.s.

  I'm learning Scala and I want to know the best way of expressing this imperative pattern using Scala's functional programming capabilities. def f(l: List[Int]): Boolean = { for (e <- l) { if (test(e)) return true } } return false } The best I can come up with is along the lines of: l map { e => test(e) } contains true But this is less efficient since it calls test() on each element, whereas the imperative version stops on the first element that satisfies test(). Is there a more idiomatic functional programming technique I can use to the same effect? The imperative version seems awkward in Scala.

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• How to kill a thread immediately from another thread in java?

  - by Sara

  Hi, is there anyway to kill a thread or interrupt it immediately. Like in one of my thread, i call a method which takes time to execute (2-4 seconds). This method is in a while(boolean flag) block, so i can interrupt it from the main thread. But the problem is, if i interrupt it; it will wait till the executing loop is finished and then on next conditional check, it will stop execution. I want it to stop right then. Is there anyway to do this?

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• Help with getParent() downcast.

  - by Preformed Cone

  I'm learning android/java and have this example code I can't get to work: OnRatingBarChangeListener l = new OnRatingBarChangeListener() { public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromTouch) { Integer myPos=(Integer)ratingBar.getTag(); RowModel model=getModel(myPos); model.rating = rating; LinearLayout p=(LinearLayout)ratingBar.getParent(); TextView l=(TextView)p.findViewById(R.id.label); l.setText(model.toString()); } }; Everything works except the LinearLayout / getParent() downcast. At runtime it creates a ClassCastException. If I comment out that block of code then everthing works fine. What am I missing?

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• Matching Line Boundaries in a Regular Expression (Pattern.MULTILINE/(?m)) is broken in Java?

  - by Mister M. Bean

  The example on http://www.exampledepot.com/egs/java.util.regex/Line.html gives false for me twice but should'nt! Why? CharSequence inputStr = "abc\ndef"; String patternStr = "abc$"; // Compile with multiline enabled Pattern pattern = Pattern.compile(patternStr, Pattern.MULTILINE); Matcher matcher = pattern.matcher(inputStr); boolean matchFound = matcher.find(); // true // Use an inline modifier to enable multiline mode matchFound = pattern.matches(".*abc$.*", "abc\r\ndef"); // false System.out.println(matchFound); // false matchFound = pattern.matches("(?m).*abc$.*", "abc\r\ndef"); // true System.out.println(matchFound);// false !!!!!

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• C++ detecting end of file

  - by xbonez

  I have a C++ program that is reading in info from a file, that stores info seperated by "$$$$". An example of how the file looks is: abc bcd $$$$ def $$$$ qwe gfh $$$$ How can I detect the file has ended, without using the eof() function? I have it set like this, getline(sin,temp) if (temp=="$$$$") { } After reading the last set of four dollars, how can I check the next line to ensure another set of data isn't beginning, and that the file has ended? If the file has indeed ended, I plan on using a boolean flag to terminate the while loop.

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• Getting data from JFrame AFTER the form is filled

  - by mary jane

  I'm trying to get data for my application from a form set in an external window (getDataWindow extends javax.swing.JFrame). The problem is that functions are executed before form is filled in. getDataWindow dataW=new getDataWindow(); dataW.setVisible(true); size=dataW.returnSize(); I've tried also adding additional boolean variable to getDataWindow getDataWindow dataW=new getDataWindow(); dataW.setVisible(true); while(!dataW.checkIfReady()){wait();} size=dataW.returnSize(); But it makes also the window wait (it appears but it's black inside and nothing happens). I think i should create some threads for that - I've tried to call a window making function getDataWindow in java.awt.EventQueue.invokeLater(new Runnable()) but I had to initialize dataW earlier so dataW.checkIfReady() could be called, so it is a catch 22.

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• Convert Yes/No/Null from SQL to True/False in a DataTable

  - by Scott Chamberlain

  I have a Sql Database (which I have no control over the schema) that has a Column that will have the varchar value of "Yes", "No", or it will be null. For the purpose of what I am doing null will be handled as No. I am programming in c# net 3.5 using a data table and table adapter to pull the data down. I would like to directly bind the column using a binding source to a check box I have in my program however I do not know how or where to put the logic to convert the string Yes/No/null to boolean True/False; Reading a null from the SQL server and writing back a No on a update is acceptable behavior. Any help is greatly appreciated. EDIT -- This is being developed for windows.

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• MessageBox.Show not raising HelpRequested event

  - by Trevortni

  I have a form that is showing a MessageBox using MessageBox.Show, and trying to receive events from the Help button on the MessageBox so I can execute my own code. The Microsoft documentation shows how to do this; however, using what is suggested does not work. Here's a shortened version of my code: Private Function MethodName() As Boolean AddHandler Me.HelpRequested, AddressOf Me.MsgBoxHelpRequested Select Case MessageBox.Show("Text", "Title", MessageButtons.YesNoCancel, MessageBoxIcon.Question, MessageBoxDefaultButton.Button2, 0, True) Case MsgBoxResult.Yes ' Do stuff Case MsgBoxResult.No ' Do stuff Case MsgBoxResult.Cancel RemoveHandler Me.HelpRequested, AddressOf Me.MsgBoxHelpRequested Return False End Select RemoveHandler Me.HelpRequested, AddressOf Me.MsgBoxHelpRequested End Function Private Sub MsgBoxHelpRequested(ByVal sender As Object, ByVal hlpevent As System.Windows.Forms.HelpEventArgs) ' Breakpoint that never gets hit ' More code End Sub I've been searching for a solution to this problem, but the best I've found is this question: http://stackoverflow.com/questions/2407880/how-to-detect-help-button-press-in-windows-forms-messagebox that refers me back to the same Microsoft code that doesn't seem to be working. Can anybody help me with this? Thank you.

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• Copying files from one directory to another in Java

  - by user42155

  Hello, I want to copy files from one directory to another (subdirectory) using Java. I have a directory, dir, with text files. I iterate over the first 20 files in dir, and want to copy them to another directory in the dir directory, which I have created right before the iteration. In the code, I want to copy the review (which represents the ith text file or review) to trainingDir. How can I do this? There seems not to be such a function (or I couldn't find). Thank you. boolean success = false; File[] reviews = dir.listFiles(); String trainingDir = dir.getAbsolutePath() + "/trainingData"; File trDir = new File(trainingDir); success = trDir.mkdir(); for(int i = 1; i <= 20; i++) { File review = reviews[i]; }

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• C++ Translation Phase Confusion

  - by blakecl

  Can someone explain why the following doesn't work? int main() // Tried on several recent C++ '03 compilers. { #define FOO L const wchar_t* const foo = FOO"bar"; // Will error out with something like: "identifier 'L' is undefined." #undef FOO } I thought that preprocessing was done in an earlier translation phase than string literal operations and general token translation. Wouldn't the compiler be more or less seeing this: int main() { const wchar_t* const foo = L"bar"; } It would be great if someone could cite an explanation from the standard.

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• Proper usage of Java Weak Reference in case of nested collections

  - by Tong Wang

  I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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• Integer v/s int

  - by Siddhartha

  Read this on the oracle docs java.lang page: Frequently it is necessary to represent a value of primitive type as if it were an object. The wrapper classes Boolean, Character, Integer, Long, Float, and Double serve this purpose. I'm not sure I understand why these are needed. It says they have useful functions such as equals(). But if I can do (a==b), why would I ever want to declare them as Integer, use more memory and use equals()? How does the memory usage differ for the 2?

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• What is a simple C library for a set of integer sets?

  - by conradlee

  I've got to modify a C program and I need to include a set of unsigned integer sets. That is, I have millions of sets of integers (each of these integer sets contains between 3 and 100 integers), and I need to store these in some structure, lets call it the directory, that can in logarithmic time tell me whether a given integer set already exists in the directory. The only operations that need to be defined on the directory is lookup and insert. This would be easy in languages with built-in support for useful data structures, but I'm a foreigner to C and looking around on Google did (surprisingly) not answer my question satisfactorily. This project looks about right: http://uthash.sourceforge.net/ but I would need to come up with my own hash key generator. This is a standard, simple problem, so I hope there is a standard and simple solution.

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• Android: Touch seriously slowing my application

  - by Jason Rogers

  Hi all, I've been raking my brains on this one for a while. when I'm running my application (opengl game) eveyrthing goes fine but when I touch the screen my application slows down quite seriously (not noticeable on powerful phones like the nexus one, but on the htc magic it gets quite annoying). I did a trace and found out that the touch events seem to be handled in a different thread and even if it doesn't take so much processing time I think androids ability to switch between threads is not so good... What is the best way to handle touch when speed is an issue ? Currently I'm using : in the GLSurfaceView @Override public boolean onTouchEvent(MotionEvent event) { GameHandler.onTouchEvent(event); return true; } Any ideas are welcome

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• Identify a non-computer network device?

  - by Avilan

  I'm current working on a program that scans my network and discoveres computers and devices on the network. I use various operations to find data on the devices I discover, but want to distinguish the network devices from computers. And I'm wondering if anyone knows how I could do this? I looked a bit at SNMP, and tried connecting to my network printer, router and modem. But I seem to only be able to connect to the printer, neither the router or modem responds. Is there another way to identify what kind of a device an IP address belongs to?

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• importing data using get or create - identity error 1062

  - by hamackey

  I am importing data from a mssql database into mysql. Works except when it encounters the id of a previous entry. id is unique. I need to get entries that already exist so that they can be placed in the work of the day. Error is IntegrityError: (1062, "Duplicate entry '001355338' for key 2") This entry is already in the database. I need it entered for that day, but can not have it added to the table. It is already there. def handle(self, *args, **options): 59 #patients_local = Patient.objects.all() 60 #attendings_local = Attending.objects.all() 61 connection = pyodbc.connect("XXXXXXXXXXX") 62 cursor = connection.cursor() 63 cursor.execute(COMMAND) 64 rows = cursor.fetchall() 65 for row in rows: 66 # get_or_create returns (object, boolean) 67 p, created = Patient.objects.get_or_create( 68 first_name = row.Firstname, 69 middle_name = '', 70 last_name = row.Lastname, 71 id = row.id, 72 )

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• Hibernate Hql find result size for paginator

  - by KCore

  Hi, I need to add paginator for my Hibernate application. I applied it to some of my database operations which I perform using Criteria by setting Projection.count().This is working fine. But when I use hql to query, I can't seem to get and efficient method to get the result count. If I do query.list().size() it takes lot of time and I think hibernate does load all the objects in memory. Can anyone please suggest an efficient method to retrieve the result count when using hql?

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• Spring MVC 3.1 How to access HttpSession in Custom Authentication Provider (which implements AuthenticationProvider)

  - by user1506231

  My application calls a web service during the Authentication process (as shown in code below). How can I save some information in HttpSession during this process? This information like customer-account-number will be used in various other places in the application after the user is logged in. Is it possible to pass HttpSession parameter to the MyServiceManager's static login method? public class MyAuthenticationManager implements AuthenticationProvider { @Override public boolean supports(Class<? extends Object> authentication) { return authentication.equals(UsernamePasswordAuthenticationToken.class); } @Override public Authentication authenticate(Authentication authentication) { //MyServiceManager.login - makes a call to web service if(MyServiceManager.login(authentication.getName(), authentication.getCredentials().toString(), XXX_HTTP_SESSION_XXX)) { List<GrantedAuthority> authorities = new ArrayList<GrantedAuthority> (); authorities.add(new GrantedAuthorityImpl("ROLE_USER")); authorities.add(new GrantedAuthorityImpl("ROLE_SUPERVISOR")); return new UsernamePasswordAuthenticationToken(authentication.getName(), authentication.getCredentials(),authorities); } else { return null; } } }

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• Why timed lock doesnt throws a timeout exception in C++0x?

  - by Vicente Botet Escriba

  C++0x allows to lock on a mutex until a given time is reached, and return a boolean stating if the mutex has been locked or not. template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); In some contexts, I consider an exceptional situation that the locking fails because of timeout. In this case an exception should be more appropriated. To make the difference a function lock_until could be used to get a timeout exception when the time is reached before locking. template <class Clock, class Duration> void lock_until(const chrono::time_point<Clock, Duration>& abs_time); Do you think that lock_until should be more adequate in some contexts? if yes, on which ones? If no, why try_lock_until will always be a better choice?

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