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• question about function derivatives

  - by davit-datuashvili

  hi i have question for example i have some function int sumefunction(//parameters here let say int x){ return something let say x*x+2*x+3 or does not matter } i am interesting how find derivative of this function ?if i have int f(int x){ return sin(x); } after derivative it must return cos(x) thanks

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• how to pass an array from a asp.net mvc controller action back to javascript using jquery / ajax

  - by oo

  Here is my jQuery code: $.get('/Home/GetList', function(data) { debugger; $('#myMultiSelect').val(values); }); Here is my controller code: public ActionResult GetList(int id) { int[] bodyParts = _repository.GetList(id); //how do i return this as an array back to javascript ?? } if I have the GetList function return an array of integers, how do I return this to the jQuery function?

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• TPL - Using static method vs struct method

  - by Sunit

  I have about 1500 files on a share for which I need to collect FileVersionInfo string. So I created a Static method in my Gateway like this: private static string GetVersionInfo(string filepath) { FileVersionInfo verInfo = FileVersionInfo.GetVersionInfo(filepath); return string.Format("{0}.{1}.{2}.{3}", verInfo.ProductMajorPart, verInfo.ProductMinorPart, verInfo.ProductBuildPart, verInfo.ProductPrivatePart).Trim(); } And then used FileAndVersion struct in a PLINQ call with DegreeOfParallelism as this is I/O related resultList = dllFilesRows.AsParallel().WithDegreeOfParallelism(20) .Select(r => { var symbolPath = r.Filename; return new FilenameAndVersion{Filename=symbolPath, Version=GetVersionInfo(symbolPath)}; }) .ToArray(); Later I modified the Struct, FileAndVersion as: private struct FilenameAndVersion { private string _version, _filename; public string Version { get { return _version; } } public string Filename { get { return _filename; } } public void SetVersion() { FileVersionInfo verInfo = FileVersionInfo.GetVersionInfo(this.Filename); this._version = string.Format("{0}.{1}.{2}.{3}", verInfo.ProductMajorPart, verInfo.ProductMinorPart, verInfo.ProductBuildPart, verInfo.ProductPrivatePart).Trim(); } public FilenameAndVersion(string filename, string version) { this._filename = filename; this._version = string.Empty; SetVersion(); } } And used it: resultList = dllFilesRows.AsParallel().WithDegreeOfParallelism(20) .Select(r => { var symbolPath = r.Filename; return new FilenameAndVersion(symbolPath, String.Empty); }) .ToArray(); The question is, is this going to help me in anyway and is a good pattern to use ? Sunit

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• How to read the values returned by the Json?

  - by user281180

  I have the following code in my view: <% using (Ajax.BeginForm("JsonCreate", new AjaxOptions { OnComplete = "createCategoryComplete" })) { % Add new category <%=Html.TextBox("CategoryId")% <%=Html.TextBox("Test")% Name: <%= Html.TextBox("Name")% <%= Html.ValidationMessage("Name")% </p> <p> <input type="submit" value="Create" /> </p> </fieldset> </div> <% } % In the controller the code is as follows: [AcceptVerbs(HttpVerbs.Post)] public JsonResult JsonCreate(string Name) { if (ModelState.IsValid) { try { //Return a json object to the javascript return Json(new { CategoryId = 123, Test= "test successful" }); } catch { #region Log errors about the exception //Log error to administrator here #endregion } } //If we got this far, something failed, return an empty json object return Json(new { /* Empty object */ }); } What should be the code in the view for the following function to read the values returned by the Json and update the textboxes for CategoryId and Test? function createCategoryComplete() {....???}

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• A good way to write unit tests

  - by bobobobo

  So, I previously wasn't really in the practice of writing unit tests - now I kind of am and I need to check if I'm on the right track. Say you have a class that deals with math computations. class Vector3 { public: // Yes, public. float x,y,z ; // ... ctors ... } ; Vector3 operator+( const Vector3& a, const Vector3 &b ) { return Vector3( a.x + b.y /* oops!! hence the need for unit testing.. */, a.y + b.y, a.z + b.z ) ; } There are 2 ways I can really think of to do a unit test on a Vector class: 1) Hand-solve some problems, then hard code the numbers into the unit test and pass only if equal to your hand and hard-coded result bool UnitTest_ClassVector3_operatorPlus() { Vector3 a( 2, 3, 4 ) ; Vector3 b( 5, 6, 7 ) ; Vector3 result = a + b ; // "expected" is computed outside of computer, and // hard coded here. For more complicated operations like // arbitrary axis rotation this takes a bit of paperwork, // but only the final result will ever be entered here. Vector3 expected( 7, 9, 11 ) ; if( result.isNear( expected ) ) return PASS ; else return FAIL ; } 2) Rewrite the computation code very carefully inside the unit test. bool UnitTest_ClassVector3_operatorPlus() { Vector3 a( 2, 3, 4 ) ; Vector3 b( 5, 6, 7 ) ; Vector3 result = a + b ; // "expected" is computed HERE. This // means all you've done is coded the // same thing twice, hopefully not having // repeated the same mistake again Vector3 expected( 2 + 5, 6 + 3, 4 + 7 ) ; if( result.isNear( expected ) ) return PASS ; else return FAIL ; } Or is there another way to do something like this?

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• Is it possible to create a Service that listens for hardware key presses?

  - by VoteBrian

  I'd like to run an Android background service that will act as a keylistener from the home screen or when the phone is asleep. Is this possible? From semi-related examples online, I put together the following service, but get the error, "onKeyDown is undefined for the type Service" public class ServiceName extends Service { @Override public void onCreate() { //Stuff } public IBinder onBind(Intent intent) { //Stuff return null; } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if(event.getAction() == KeyEvent.ACTION_DOWN) { switch(keyCode) { case KeyEvent.KEYCODE_A: //Stuff return true; case KeyEvent.KEYCODE_B: //Stuff return true; //etc. } } return super.onKeyDown(keyCode, event); } } I realize Android defaults to the search bar when you type from the home screen, but this really is just for a very particular use. I don't really expect to distribute this. Also, it'd be nice to use the camera button to wake the phone.

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• Is there a way to make sure classes implementing an Interface implement static methods?

  - by Tobias Kienzler

  Frist of all, I read erickson's usefull reply to "Why can’t I define a static method in a Java interface?". This question is not about the "why" but about the "how then?". So basically I want one Interface to provide both usual methods and e.g. a getSimilarObject method. For (a made up) example public interface ParametricFunction { /** @return f(x) using the parameters */ static abstract public double getValue(double x, double[] parameters); /** @return The function's name */ static abstract public String getName(); } and then public class Parabola implements ParametricFunction { /** @return f(x) = parameters[0] * x² + parameters[1] * x + parameters[2] */ static public double getValue(double x, double[] parameters) { return ( parameters[2] + x*(parameters[1] + x*parameters[0])); } static public String getName() { return "Parabola"; } } Since this is not allowed in the current Java standard, what is the closest thing to this? The idea behind this is putting several ParametricFunction's in a package and use Reflection to list them all, allowing the user to pick e.g. which one to plot. Obviously one could provide a loader class containing an array of the available ParametricFunction's, but every time a new one is implemented one has to remember adding it there, too.

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• JQuery URL Validator

  - by Vincent

  All, I am trying to use JQuery's URL Validator plugin. http://docs.jquery.com/Plugins/Validation/Methods/url I have a text box that has a URL. I want to write a function which takes the textbox value, uses the jquery's validator plugin to validate urls and returns true or false. Something like Ex: function validateURL(textval) { // var valid = get jquery's validate plugin return value if(valid) { return true; } return false; } I wanted this to be a reusable function.. Thanks

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• Win32 reset event like synchronization class with boost C++

  - by fgungor

  I need some mechanism reminiscent of Win32 reset events that I can check via functions having the same semantics with WaitForSingleObject() and WaitForMultipleObjects() (Only need the ..SingleObject() version for the moment) . But I am targeting multiple platforms so all I have is boost::threads (AFAIK) . I came up with the following class and wanted to ask about the potential problems and whether it is up to the task or not. Thanks in advance. class reset_event { bool flag, auto_reset; boost::condition_variable cond_var; boost::mutex mx_flag; public: reset_event(bool _auto_reset = false) : flag(false), auto_reset(_auto_reset) { } void wait() { boost::unique_lock<boost::mutex> LOCK(mx_flag); if (flag) return; cond_var.wait(LOCK); if (auto_reset) flag = false; } bool wait(const boost::posix_time::time_duration& dur) { boost::unique_lock<boost::mutex> LOCK(mx_flag); bool ret = cond_var.timed_wait(LOCK, dur) || flag; if (auto_reset && ret) flag = false; return ret; } void set() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = true; cond_var.notify_all(); } void reset() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = false; } }; Example usage; reset_event terminate_thread; void fn_thread() { while(!terminate_thread.wait(boost::posix_time::milliseconds(10))) { std::cout << "working..." << std::endl; boost::this_thread::sleep(boost::posix_time::milliseconds(1000)); } std::cout << "thread terminated" << std::endl; } int main() { boost::thread worker(fn_thread); boost::this_thread::sleep(boost::posix_time::seconds(1)); terminate_thread.set(); worker.join(); return 0; } EDIT I have fixed the code according to Michael Burr's suggestions. My "very simple" tests indicate no problems. class reset_event { bool flag, auto_reset; boost::condition_variable cond_var; boost::mutex mx_flag; public: explicit reset_event(bool _auto_reset = false) : flag(false), auto_reset(_auto_reset) { } void wait() { boost::unique_lock<boost::mutex> LOCK(mx_flag); if (flag) { if (auto_reset) flag = false; return; } do { cond_var.wait(LOCK); } while(!flag); if (auto_reset) flag = false; } bool wait(const boost::posix_time::time_duration& dur) { boost::unique_lock<boost::mutex> LOCK(mx_flag); if (flag) { if (auto_reset) flag = false; return true; } bool ret = cond_var.timed_wait(LOCK, dur); if (ret && flag) { if (auto_reset) flag = false; return true; } return false; } void set() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = true; cond_var.notify_all(); } void reset() { boost::lock_guard<boost::mutex> LOCK(mx_flag); flag = false; } };

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• java template design

  - by Sean Nguyen

  Hi, I have this class: public class Converter { private Logger logger = Logger.getLogger(Converter.class); public String convert(String s){ if (s == null) throw new IllegalArgumentException("input can't be null"); logger.debug("Input = " + s); String r = s + "abc"; logger.debug("Output = " + s); return r; } public Integer convert(Integer s){ if (s == null) throw new IllegalArgumentException("input can't be null"); logger.debug("Input = " + s); Integer r = s + 10; logger.debug("Output = " + s); return r; } } The above 2 methods are very similar so I want to create a template to do the similar things and delegate the actual work to the approriate class. But I also want to easily extends this frame work without changing the template. So for example: public class ConverterTemplate { private Logger logger = Logger.getLogger(Converter.class); public Object convert(Object s){ if (s == null) throw new IllegalArgumentException("input can't be null"); logger.debug("Input = " + s); Object r = doConverter(); logger.debug("Output = " + s); return r; } protected abstract Object doConverter(Object arg); } public class MyConverter extends ConverterTemplate { protected String doConverter(String str) { String r = str + "abc"; return r; } protected Integer doConverter(Integer arg) { Integer r = arg + 10; return r; } } But that doesn't work. Can anybody suggest me a better way to do that? I want to achieve 2 goals: 1. A template that is extensible and does all the similar work for me. 2. I ant to minimize the number of extended class. Thanks,

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• JavaScript Regex question

  - by Vincent

  All, I have following function to check for invalid symbols entered in a text box and return true or false. How can I modify this function to also check for occurrences like http:// and https:// and ftp:// return false if encountered ? function checkURL(textboxval) { return ! (/[<>()#'"]|""/.test(textboxval)); } Thanks

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• Factory Method Using Is/As Operator

  - by Swim

  I have factory that looks something like the following snippet. Foo is a wrapper class for Bar and in most cases (but not all), there is a 1:1 mapping. As a rule, Bar cannot know anything about Foo, yet Foo takes an instance of Bar. Is there a better/cleaner approach to doing this? public Foo Make( Bar obj ) { if( obj is Bar1 ) return new Foo1( obj as Bar1 ); if( obj is Bar2 ) return new Foo2( obj as Bar2 ); if( obj is Bar3 ) return new Foo3( obj as Bar3 ); if( obj is Bar4 ) return new Foo3( obj as Bar4 ); // same wrapper as Bar3 throw new ArgumentException(); } At first glance, this question might look like a duplicate (maybe it is), but I haven't seen one exactly like it. Here is one that is close, but not quite: http://stackoverflow.com/questions/242097/factory-based-on-typeof-or-is-a

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• Concatenate, sort and swap array in Java

  - by sblck

  I am trying to concatenate two arrays into new array, sort in order, and swap two values of index. I'm kind of new to java and only use C before so having a hard time handling an Object. In main method it declares two object arrays IntVector vector = new IntVector(3); and IntVector vector2 = new IntVector(3); I can only do this if the types are int[], but I want to use as an object How should I code the concat, sort, and swap method? public class IntVector { private int[] items_; private int itemCount_; private IntVector(int[] data, int n) { items_ = data.clone(); itemCount_ = n; } public IntVector(int itemSize) { itemCount_ =0; if(itemSize<1) itemSize =10; items_ = new int[itemSize]; } public void push(int value) { if(itemCount_ + 1 >= items_.length) overflow(); items_[itemCount_++] = value; } public void log() { for (int i=0 ; i<itemCount_; ++i) { System.out.print(items_[i]); if(i<itemCount_ -1) System.out.println(); } } public void overflow() { int[] newItems = new int[items_.length * 2]; for(int i=0 ; i<itemCount_; ++i) { newItems[i] = items_[i]; } items_=newItems; } public int getValue(int index) { if(index < 0 || index >= itemCount_) { System.out.println("[error][IntVector][setValue] Incorrect index=" + index); return 0; } return items_[index]; } public void setValue(int index, int value) { if(index < 0 || index >= itemCount_) { System.out.println("[error][IntVector][setValue] Incorrect index=" + index); return ; } items_[index] = value; } public IntVector clone() { return new IntVector(items_, itemCount_); } public IntVector concat() { return null; } public IntVector sort() { return null; } public IntVector swap() { return null; } public static void main(String[] args) { IntVector vector = new IntVector(3); IntVector vector2 = new IntVector(3); vector.push(8); vector.push(200); vector.push(3); vector.push(41); IntVector cloneVector = vector.clone(); vector2.push(110); vector2.push(12); vector2.push(7); vector2.push(141); vector2.push(-32); IntVector concatResult = vector.concat(vector2); IntVector sortResult = concatResult.sort(); IntVector swapResult = sortResult.clone(); //swapResult.swap(1,5); System.out.print("vector : "); vector.log(); System.out.print("\n\ncloneVector : "); cloneVector.log(); System.out.print("\n\nvector2 : "); vector2.log(); System.out.print("\n\nconcatvector : "); concatResult.log(); System.out.print("vector : "); vector.log(); System.out.print("vector : "); vector.log(); } }

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• modify a method/function at runtime

  - by mononym

  I've been looking at the php reflection methods, what i want to do is inject some code after the method is opened and before any return value, for example i want to change: function foo($bar) { $foo = $bar ; return $foo ; } And inject some code into it like: function foo($bar) { //some code here $foo = $bar ; //some code here return $foo ; } possible?

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• how am I supposed to call the function?

  - by user1816768

  I wrote a program which tells you knight's movement (chess). For example if I wanted to know all possible moves, I'd input: possibilites("F4") and I'd get ['D3', 'D5', 'E2', 'E6', 'G2', 'G6', 'H3', 'H5'] as a result, ok I did that, next, I had to write a function in which you input two fields and if those fields are legal, you'd get True and if they're not you'd get False(I had to use the previous function). For example: legal("F4","D3") >>>True code: def legal(field1,field2): c=possibilities(field1) if field1 and field2 in a: return True return False I'm having a problem with the following function which I have to write: I have to put in path of the knight and my function has to tell me if it's legal path, I'm obliged to use the previous function. for example: >>> legal_way(["F3", "E1", "G2", "H4", "F5"]) True >>> legal_way(["F3", "E1", "G3", "H5"]) False >>> legal_way(["B4"]) True I know I have to loop through the list and put first and second item on it in legal(field1,field2) and if it's false, everything is false, but if it's true I have to continue to the end, and this has to work also if I have only one field. I'm stuck, what to do? def legal_way(way): a=len(way) for i in range(0,a-2): if a==1: return true else if legal(way[i],way[i+1]: return True return False and I get True or index out of range

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• c# ProcessCmdKey overload, match generic combination

  - by leo

  Hi all, On some control, I want ProcessCmdKey to return true if the keys pressed by the user were ALT and any letter of the alphabet. I'm able to return true if the user presses Alt with the following code, but how can I add the condition of a letter also pressed ? protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { if ((keyData & Keys.Alt) != 0) { return true; } } Thanks.

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• Extending appengine's db.Property with caching

  - by Noio

  I'm looking to implement a property class for appengine, very similar to the existing db.ReferenceProperty. I am implementing my own version because I want some other default return values. My question is, how do I make the property remember its returned value, so that the datastore query is only performed the first time the property is fetched? What I had is below, and it does not work. I read that the Property classes do not belong to the instances, but to the model definition, so I guess that the return value is not cached for each instance, but overwritten on the model every time. Where should I store this _resolved variable? class PageProperty(db.Property): data_type = Page def get_value_for_datastore(self, model_instance): page = super(PageProperty, self).get_value_for_datastore(model_instance) self._resolved = page return page.key().name() def make_value_from_datastore(self, value): if not hasattr(self, '_resolved'): self._resolved = Page.get_by_name(value) return self._resolved

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• template; operator (int)

  - by Oops

  Hi, regarding my Point struct already mentioned here: http://stackoverflow.com/questions/2794369/template-class-ctor-against-function-new-c-standard is there a chance to replace the function toint() with a cast-operator (int)? namespace point { template < unsigned int dims, typename T > struct Point { T X[ dims ]; //umm??? template < typename U > Point< dims, U > operator U() const { Point< dims, U > ret; std::copy( X, X + dims, ret.X ); return ret; } //umm??? Point< dims, int > operator int() const { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } //OK Point<dims, int> toint() { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } }; //struct Point template < typename T > Point< 2, T > Create( T X0, T X1 ) { Point< 2, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; return ret; } }; //namespace point int main(void) { using namespace point; Point< 2, double > p2d = point::Create( 12.3, 34.5 ); Point< 2, int > p2i = (int)p2d; //äähhm??? std::cout << p2d.str() << std::endl; char c; std::cin >> c; return 0; } I think the problem is here that C++ cannot distinguish between different return types? many thanks in advance. regards Oops

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• Full automatic application trace for .net v4

  - by JL

  I would like to implement a way to trace every line of code in an application that is written for .net v4.0. An example would be. If I had the following function. private bool hasValue(string value) { if(string.isnullorempty(value) { return false; } else { return true; }} Then when the function is called I want detailed trace logs to contain something like this: Function called |Line 10 |Signature private bool hasValue(string value)|ValuesPassed hasValue("") Line Evaluated | Line 11 | if(string.isnullorempty(value) |ValuesPassed if(string.isnullorempty("") - evaluation returned true entered line 13 |signature return false|return action taken. This tracing can be done manually, but its a lot of work, and would dirty the code. Isn't there a way to get this level of tracing automatically with .net or 3rd party plugin? Thank you

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• Is it possible to write a generic +1 method for numeric box types in Java?

  - by polygenelubricants

  This is NOT homework. Part 1 Is it possible to write a generic method, something like this: <T extends Number> T plusOne(T num) { return num + 1; // DOESN'T COMPILE! How to fix??? } Short of using a bunch of instanceof and casts, is this possible? Part 2 The following 3 methods compile: Integer plusOne(Integer num) { return num + 1; } Double plusOne(Double num) { return num + 1; } Long plusOne(Long num) { return num + 1; } Is it possible to write a generic version that bound T to only Integer, Double, or Long?

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• calling a trim method in actionscript 2.0

  - by user151013

  Hi I Got a notnull function for a text field as below private function valStringNotNull( val:String ) :Boolean { if ( String(val).length <= 0 ) { _errorCode = "StringNull"; return false; } _errorCode = "NoError"; return true; } and this function is being called here var pCnt:Number = 0; _validateParams[pCnt++] = { type: "notNull", input: win.firstNameInput , isSendData:true, dataName:"firstName"}; _validateParams[pCnt++] = { type: "notNull", input: win.lastNameInput, isSendData:true, dataName:"lastName"}; _validateParams[pCnt++] = { type: "noValidation", input: roleCombo, isSendData:true, dataName:"role" }; Selection.setFocus(win.firstNameInput); and for the not null I defined this way private function validateCases ( param:Object ) :Boolean { _errorObj = param.input || param.input1; switch( param.type ) { case "notNull": return valStringNotNull( param.input.text ); break; } } but as you see as I defined the length should be greater than zero its taking even a space as an input and displaying blank white space in my text field so I got a trim function as below public function ltrim(input:String):String { var size:Number = input.length; for(var i:Number = 0; i < size; i++) { if(input.charCodeAt(i) > 32) { return input.substring(i); } } return ""; } and I need to call this trim function before my not null function so that it trims off all the leftside white space but as I am very new to flash can some one help me how to keep this trim function before the notnull function.Can some one please help me with this please

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• How to remove .zip file in c on windows? (error: Directory not empty)

  - by ExtremeBlue

  include include include include "win32-dirent.h" include include include define MAXFILEPATH 1024 bool IsDirectory(char* path) { WIN32_FIND_DATA w32fd; HANDLE hFindFile; hFindFile = FindFirstFile((PTCHAR)path, &w32fd); if(hFindFile == INVALID_HANDLE_VALUE) { return false; } return w32fd.dwFileAttributes & (FILE_ATTRIBUTE_DIRECTORY); } int RD(const char* folderName) { DIR *dir; struct dirent *ent; dir = opendir(folderName); if(dir != NULL) { while((ent = readdir(dir)) != NULL) { if(strcmp(ent->d_name , ".") == 0 || strcmp(ent->d_name, "..") == 0) { continue; } char fileName[MAXFILEPATH]; sprintf(fileName,"%s%c%s", folderName, '\\', ent->d_name); if(IsDirectory(fileName)) { RD(fileName); } else { unlink(fileName); } } closedir(dir); //chmod(folderName, S_IWRITE | S_IREAD); if(_rmdir(folderName) != 0)perror(folderName); } else { printf("%s <%s>\n","Could Not Open Directory.", folderName); return -1; } return 0; } int main(int argc, char* argv[]) { if(argc < 2) { printf("usage: ./a.out \n"); return 1; } //RD(argv[1]); //_mkdir("12"); //_mkdir("12\\34"); //_rmdir("12\\34"); //_rmdir("12"); char buf[0xff]; sprintf(buf, "unzip -x -q -d 1234 1234.zip"); system(buf); RD("1234"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\56\\5.txt"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\56\\6.txt"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\1_23.zip"); //unlink("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\4.txt"); //_rmdir("D:\\dev\\c\\project\\removeFolder\\Debug\\1234\\56"); //_rmdir("D:\\dev\\c\\project\\removeFolder\\Debug\\1234"); return 0; } Archive: 1234.zip inflating: 1234/4.txt inflating: 1234/56/5.txt inflating: 1234/56/6.txt inflating: 1234/1_23.zip

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• How to use method hiding (new) with generic constrained class

  - by ongle

  I have a container class that has a generic parameter which is constrained to some base class. The type supplied to the generic is a sub of the base class constraint. The sub class uses method hiding (new) to change the behavior of a method from the base class (no, I can't make it virtual as it is not my code). My problem is that the 'new' methods do not get called, the compiler seems to consider the supplied type to be the base class, not the sub, as if I had upcast it to the base. Clearly I am misunderstanding something fundamental here. I thought that the generic where T: xxx was a constraint, not an upcast type. This sample code basically demonstrates what I'm talking about. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace GenericPartialTest { class ContextBase { public string GetValue() { return "I am Context Base: " + this.GetType().Name; } public string GetOtherValue() { return "I am Context Base: " + this.GetType().Name; } } partial class ContextSub : ContextBase { public new string GetValue() { return "I am Context Sub: " + this.GetType().Name; } } partial class ContextSub { public new string GetOtherValue() { return "I am Context Sub: " + this.GetType().Name; } } class Container<T> where T: ContextBase, new() { private T _context = new T(); public string GetValue() { return this._context.GetValue(); } public string GetOtherValue() { return this._context.GetOtherValue(); } } class Program { static void Main(string[] args) { Console.WriteLine("Simple"); ContextBase myBase = new ContextBase(); ContextSub mySub = new ContextSub(); Console.WriteLine(myBase.GetValue()); Console.WriteLine(myBase.GetOtherValue()); Console.WriteLine(mySub.GetValue()); Console.WriteLine(mySub.GetOtherValue()); Console.WriteLine("Generic Container"); Container<ContextBase> myContainerBase = new Container<ContextBase>(); Container<ContextSub> myContainerSub = new Container<ContextSub>(); Console.WriteLine(myContainerBase.GetValue()); Console.WriteLine(myContainerBase.GetOtherValue()); Console.WriteLine(myContainerSub.GetValue()); Console.WriteLine(myContainerSub.GetOtherValue()); Console.ReadKey(); } } }

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• Should we use p(..) or (*p)(..) when p is a function pointer?

  - by q0987

  Reference: [33.11] Can I convert a pointer-to-function to a void*? #include "stdafx.h" #include <iostream> int f(char x, int y) { return x; } int g(char x, int y) { return y; } typedef int(*FunctPtr)(char,int); int callit(FunctPtr p, char x, int y) // original { return p(x, y); } int callitB(FunctPtr p, char x, int y) // updated { return (*p)(x, y); } int _tmain(int argc, _TCHAR* argv[]) { FunctPtr p = g; // original std::cout << p('c', 'a') << std::endl; FunctPtr pB = &g; // updated std::cout << (*pB)('c', 'a') << std::endl; return 0; } Question Which way, the original or updated, is the recommended method? Thank you Although I do see the following usage in the original post: void baz() { FredMemFn p = &Fred::f; ? declare a member-function pointer ... }

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• Problems with 'while' loop and 'for' loop when reading through file

  - by David Beckham

  I wasted plenty of hours trying to figure out the problem but no luck. Tried asking the TA at my school, but he was useless. I am a beginner and I know there are a lot of mistakes in it, so it would be great if I can get some detail explanation as well. Anyways, basically what I am trying to do with the following function is: Use while loop to check and see if random_string is in TEXT, if not return NoneType if yes, then use a for loop to read lines from that TEXT and put it in list, l1. then, write an if statement to see if random_string is in l1. if it is, then do some calculations. else read the next line Finally, return the calculations as a whole. TEXT = open('randomfile.txt') def random (TEXT, random_string): while random_string in TEXT: for lines in TEXT: l1=TEXT.readline().rsplit() if random_string in l1: ''' do some calculations ''' else: TEXT.readline() #read next line??? return #calculations return None

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