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• Solving problems with near infinite potential solutions

  - by Zonda333

  Today I read the following problem: Use the digits 2, 0, 1, 1 and the operations +, -, x, ÷, sqrt, ^ , !, (), combinations, and permutations to write equations for the counting numbers 1 through 100. All four digits must be used in each expression. Only the digits 2, 0, 1, 1 may be used, and each must be used exactly once. Decimals may be used, as in .1, .02, etc. Digits may be combined; numbers such as 20 or 101 may be used. Example: 60 = 10*(2+1)!, 54 = ¹¹C2 - 0! Though I was able to quickly find around 50 solutions quite easily in my head, I thought programming it would be a far superior solution. However, I then realized I had no clue how to go about solving a problem like this. I am not asking for complete code for me to copy and paste, but for ideas about how I would solve this problems, and others like it that have nearly infinite potential solutions. As I will be writing it in python, where I have the most experience, I would prefer if the answers were more python based, but general ideas are great too.

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• Updating Cells in a DataTable

  - by Maxim Z.

  I'm writing a small app to do a little processing on some cells in a CSV file I have. I've figured out how to read and write CSV files with a library I found online, but I'm having trouble: the library parses CSV files into a DataTable, but, when I try to change a cell of the table, it isn't saving the change in the table! Below is the code in question. I've separated the process into multiple variables and renamed some of the things to make it easier to debug for this question. Code Inside the loop: string debug1 = readIn.Rows[i].ItemArray[numColumnToCopyTo].ToString(); string debug2 = readIn.Rows[i].ItemArray[numColumnToCopyTo].ToString().Trim(); string debug3 = readIn.Rows[i].ItemArray[numColumnToCopyFrom].ToString().Trim(); string towrite = debug2 + ", " + debug3; readIn.Rows[i].ItemArray[numColumnToCopyTo] = (object)towrite; After the loop: readIn.AcceptChanges(); When I debug my code, I see that towrite is being formed correctly and everything's OK, except that the row isn't updated: why isn't it working? I have a feeling that I'm making a simple mistake here: the last time I worked with DataTables (quite a long time ago), I had similar problems. If you're wondering why I'm adding another comma in towrite, it's because I'm combining a street address field with a zip code field - I hope that's not messing anything up. My code is kind of messy, as I'm only trying to edit one file to make a small fix, so sorry.

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• How to easily apply a function to a collection in C++

  - by Jesse Beder

  I'm storing images as arrays, templated based on the type of their elements, like Image<unsigned> or Image<float>, etc. Frequently, I need to perform operations on these images; for example, I might need to add two images, or square an image (elementwise), and so on. All of the operations are elementwise. I'd like get as close as possible to writing things like: float Add(float a, float b) { return a+b; } Image<float> result = Add(img1, img2); and even better, things like complex ComplexCombine(float a, float b) { return complex(a, b); } Image<complex> result = ComplexCombine(img1, img2); or struct FindMax { unsigned currentMax; FindMax(): currentMax(0) {} void operator(unsigned a) { if(a > currentMax) currentMax = a; } }; FindMax findMax; findMax(img); findMax.currentMax; // now contains the maximum value of 'img' Now, I obviously can't exactly do that; I've written something so that I can call: Image<float> result = Apply(img1, img2, Add); but I can't seem to figure out a generic way for it to detect the return type of the function/function object passed, so my ComplexCombine example above is out; also, I have to write a new one for each number of arguments I'd like to pass (which seems inevitable). Any thoughts on how to achieve this (with as little boilerplate code as possible)?

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• How can I simplify this user interface?

  - by Bears will eat you

  I'm writing an internal-tools webapp; one of the central pages in this tool has a whole bunch of related commands the user can execute by clicking one of a number of buttons on the page, like this: Ideally, all of the buttons would fit on one line. Ordinarily I'd do this by changing each widget from a button with a (sometimes long) text label to a simple, compact icon - e.g. could be replaced by a familiar disk icon: Unfortunately, I don't think I can do this for every button on this particular page. Some of the command buttons just don't have good visual analogs - "VDS List". Or, if I needed to add another button in the future for some other kind of list, I'd need two icons that both communicate "list-ness" and which list. So, I'm still considering this option, but I don't love it. So it's come time for me to add yet another button to this section (don't you love internal tools?). There's not enough room on that single line to fit the new button. Aside from the icon solution I already mentioned, what would be a good* way to simplify/declutter/reduce or otherwise improve this UI? *As per Jakob Nielsen's article, I'd like to think that a dropdown menu is not the solution.

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• Learning Java and logic using debugger. Did I cheat?

  - by centr0

  After a break from coding in general, my way of thinking logically faded (as if it was there to begin with...). I'm no master programmer. Intermediate at best. I decided to see if i can write an algorithm to print out the fibonacci sequence in Java. I got really frustrated because it was something so simple, and used the debugger to see what was going on with my variables. solved it in less than a minute with the help of the debugger. Is this cheating? When I read code either from a book or someone else's, I now find that it takes me a little more time to understand. If the alghorithm is complex (to me) i end up writing notes as to whats going on in the loop. A primitive debugger if you will. When you other programmers read code, do you also need to write things down as to whats the code doing? Or are you a genius and and just retain it?

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• Complicated API issue with calling assemblies dynamically?

  - by Stefanos Tses

  I have an interesting challenge that I'm wondering if anyone here can give me some direction. I'm writing a .Net windows forms application that runs on a network and uses an SQL Server to save and pull data. I want to offer a mini "plugin" API, where developers can build their own assemblies and implement a specific interface (IDataManipulate). These assemblies then can be used by my application to call the interface functions and do something. I can create assemblies using my API, copy the file to a folder in my local hard drive and configure my application to use Reflection to call a specific function from the implemented interface (IDataManipulate.Execute). The problem: Since the application will be installed in multiple workstations in the network, is impossible to copy the plugin dlls the users will create to each machine. Solutions I tried: Solution 1 Copy the API dll to a network share. Problem: Requires AllowPartiallyTrustedCallersAttribute, which requires .Net singing, which I can't force from my users. Solution 2 (preferred) Serialize the dll object, save it to the database, deserialize it and call IDataManipulate.Execute. Problem: After deserialization, I try cast it to a IDataManipulate object but returns an error looking for the actual dll file. Solution 3 Save the dll bytes as byte[] to the database and recreate the dll at the local PC every time the user starts my application. Problem: Dll may have dependencies, which I don't know if I can detect. Any suggestions will be greatly appreciated. Thanks

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• Coding the R-ight way - avoiding the for loop

  - by mropa

  I am going through one of my .R files and by cleaning it up a little bit I am trying to get more familiar with writing the code the r-ight way. As a beginner, one of my favorite starting points is to get rid of the for() loops and try to transform the expression into a functional programming form. So here is the scenario: I am assembling a bunch of data.frames into a list for later usage. dataList <- list (dataA, dataB, dataC, dataD, dataE ) Now I like to take a look at each data.frame's column names and substitute certain character strings. Eg I like to substitute each "foo" and "bar" with "baz". At the moment I am getting the job done with a for() loop which looks a bit awkward. colnames(dataList[[1]]) [1] "foo" "code" "lp15" "bar" "lh15" colnames(dataList[[2]]) [1] "a" "code" "lp50" "ls50" "foo" matchVec <- c("foo", "bar") for (i in seq(dataList)) { for (j in seq(matchVec)) { colnames (dataList[[i]])[grep(pattern=matchVec[j], x=colnames (dataList[[i]]))] <- c("baz") } } Since I am working here with a list I thought about the lapply function. My attempts handling the job with the lapply function all seem to look alright but only at first sight. If I write f <- function(i, xList) { gsub(pattern=c("foo"), replacement=c("baz"), x=colnames(xList[[i]])) } lapply(seq(dataList), f, xList=dataList) the last line prints out almost what I am looking for. However, if i take another look at the actual names of the data.frames in dataList: lapply (dataList, colnames) I see that no changes have been made to the initial character strings. So how can I rewrite the for() loop and transform it into a functional programming form? And how do I substitute both strings, "foo" and "bar", in an efficient way? Since the gsub() function takes as its pattern argument only a character vector of length one.

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• How can I have a Label change dynamically based on a Slider Value?

  - by duney

  I'm writing a grade calculator and I currently have a slider with a textbox beside it which displays the current value of the slider: <Slider Name="gradeSlider" Grid.Row="3" Grid.Column="2" VerticalAlignment="Center" Minimum="40" Maximum="100" IsSnapToTickEnabled="True" TickFrequency="5" TickPlacement="BottomRight"/> <TextBox Name="targetGrade" Grid.Row="3" Grid.Column="3" Width="30" Height="23" Text="{Binding ElementName=gradeSlider, Path=Value}" TextAlignment="Center"/> However I'm struggling to include a label which will show display a different grade classification based on the slider's value range. I'd have thought that I could create the label: <Label Name="gradeClass" Grid.Row="2" Grid.Column="2" HorizontalAlignment="Center" VerticalAlignment="Bottom"/> And then use code: string gradeText; if (gradeSlider.Value >= 40 && gradeSlider.Value < 50) { gradeText = "Pass"; gradeClass.Content = gradeText; } else if (gradeSlider.Value >= 50 && gradeSlider.Value < 60) { gradeText = "2:2"; gradeClass.Content = gradeText; } else { gradeText = "so on..."; gradeClass.Content = gradeText; } But the label just stays as "Pass" whatever the slider value. Could somebody please advise me as to where I'm going wrong? I tried using Content = "{Binding Source = gradeText}" on the Label xaml and removing the gradeClass.Content's in the code but it complained that gradeText was declared but never used. Many thanks to anyone who can help.

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• How to speed up drawing of scaled image? Audio playback chokes during window resize.

  - by Paperflyer

  I am writing an audio player for OSX. One view is a custom view that displays a waveform. The waveform is stored as a instance variable of type NSImage with an NSBitmapImageRep. The view also displays a progress indicator (a thick red line). Therefore, it is updated/redrawn every 30 milliseconds. Since it takes a rather long time to recalculate the image, I do that in a background thread after every window resize and update the displayed image once the new image is ready. In the meantime, the original image is scaled to fit the view like this: // The drawing rectangle is slightly smaller than the view, defined by // the two margins. NSRect drawingRect; drawingRect.origin = NSMakePoint(sideEdgeMarginWidth, topEdgeMarginHeight); drawingRect.size = NSMakeSize([self bounds].size.width-2*sideEdgeMarginWidth, [self bounds].size.height-2*topEdgeMarginHeight); [waveform drawInRect:drawingRect fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1]; The view makes up the biggest part of the window. During live resize, audio starts choking. Selecting the "big" graphic card on my Macbook Pro makes it less bad, but not by much. CPU utilization is somewhere around 20-40% during live resizes. Instruments suggests that rescaling/redrawing of the image is the problem. Once I stop resizing the window, CPU utilization goes down and audio stops glitching. I already tried to disable image interpolation to speed up the drawing like this: [[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationNone]; That helps, but audio still chokes during live resizes. Do you have an idea how to improve this? The main thing is to prevent the audio from choking.

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• DateChooser is behaving strangely

  - by Tam

  I'm writing a Flex application and I came across what I think is a weird problem. I want to create a text box and a DateChooser as the datefield didn't do what I wanted and it's Halo so I can't skin it easily. I want the DateChooser to show when I click on the text input. Here is an except from my code: <s:TextInput id="wholeDate" width="100" mouseOver="stopChangeToNormal();" paddingRight="10" click="date1.visible = true" focusOut="date1.visible = false"/> <s:Button label="Go" width="70" /> </s:Panel> <mx:DateChooser id="date1" visible = "false" change="useDate(event);" mouseOver="changeToNormalState = false;" y="{wholeDate.y + buttonsGroup.y + 20}" x="{wholeDate.x + buttonsGroup.x - 175 }" /> The weird thing is that it works as I wanted if I make it visible = "true" to start but if I have it visible="false" it doesn't work! It shows but the date I select doesn't show in the box as it does if I have it as visible="true", but I don't want it to be visible initially. Any ideas?

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• setImageViewResource Sometimes loads image and sometimes it doesn't.

  - by Niv

  Hi All, I'm writing a simple widget which has an imageview widget that is supposed to load an image dynamically. To do this, I'm starting a service in the onUpdate method of the service. I validated that the service is running, however, the image is loaded only once every 10 times. Here is the code: (In the Original extends AppWidgetProvider) @Override public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) { Log.d(LOG_TAG, "onUpdate(): Starting Service..1"); context.startService(new Intent(context, UpdateService.class)); } (The service:) @Override public void onStart(Intent intent, int startId) { Log.d(LOG_TAG, "(OnStart) In On Start..!"); AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this); int[] appWidgetIds = appWidgetManager.getAppWidgetIds(new ComponentName(this, Original.class)); for (int appWidgetId : appWidgetIds) { RemoteViews remoteView = new RemoteViews(this.getPackageName(), R.layout.widget); remoteView.setImageViewResource(R.id.widgetImage, R.drawable.let02); remoteView.setTextViewText(R.id.widget_textview_month, "aaa"); Log.d(LOG_TAG, "(OnUpdate) Set All Fields!"); appWidgetManager.updateAppWidget(appWidgetId, remoteView); } //super.onStart(intent, startId); return; }

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• Is False == 0 and True == 1 in Python an implementation detail or guaranteed by the language?

  - by EOL

  Is it guaranteed that False == 0 and True == 1, in Python? For instance, is it in any way guaranteed that the following code will always produce the same results, whatever the version of Python (existing and in the foreseeable future)? 0 == False # True 1 == True # True ['zero', 'one'][False] # is 'zero' Any reference to the official documentation would be much appreciated! Other comments would be appreciated too… :) Edit: As noted in many answers, bool inherits from int. The question can therefore be recast as: "Is this an implementation detail that might change in the future, or does the documentation officially say that programmers can rely on booleans inheriting from integers?". This question is relevant for writing robust code that won't fail because of implementation details! Edit 2: The original question is still open, I believe (even though I accepted what I thought was the closest answer): even though Python 3 officially recognizes booleans as integers, I have not yet seen any official integer values for False and True… It therefore looks to me like it is best to stay clear from the assumption that False==0 and True==1.

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• Groovy and XML: Not able to insert processing instruction

  - by rhellem

  Scenario Need to update some attributes in an existing XML-file. The file contains a XSL processing instruction, so when the XML is parsed and updated I need to add the instruction before writing it to a file again. Problem is - whatever I do - I'm not able to insert the processing instruction Based on the Java-example found at rgagnon.com I have created the code below Example code ## import groovy.xml.* def xml = '''|<something> | <Settings> | </Settings> |</something>'''.stripMargin() def document = DOMBuilder.parse( new StringReader( xml ) ) def pi = document.createProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="Bp8DefaultView.xsl"'); document.insertBefore(pi, document.documentElement) println document.documentElement Creates output <?xml version="1.0" encoding="UTF-8"?> <something> <Settings> </Settings> </something> What I want <?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="Bp8DefaultView.xsl"?> <something> <Settings> </Settings> </something>

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• Beginnerquestion: How to count amount of each number drawn in a Lottery and output it in a list?

  - by elementz

  I am writing this little Lottery application. Now the plan is, to count how often each number has been drawn during each iteration of the Lottery, and store this somewhere. My guess is that I would need to use a HashMap, that has 6 keys and increments the value by one everytime the respective keys number is drawn. But how would I accomplish this? My code so far: public void numberCreator() { // creating and initializing a Random generator Random rand = new Random(); // A HashMap to store the numbers picked. HashMap hashMap = new HashMap(); // A TreeMap to sort the numbers picked. TreeMap treeMap = new TreeMap(); // creating an ArrayList which will store the pool of availbale Numbers List<Integer>numPool = new ArrayList<Integer>(); for (int i=1; i<50; i++){ // add the available Numbers to the pool numPool.add(i); hashMap.put(nums[i], 0); } // array to store the lotto numbers int [] nums = new int [6]; for (int i =0; i < nums.length; i++){ int numPoolIndex = rand.nextInt(numPool.size()); nums[i] = numPool.get(numPoolIndex); // check how often a number has been called and store the new amount in the Map int counter = hashMap.get numPool.remove(numPoolIndex); } System.out.println(Arrays.toString(nums)); } Maybe someone can tell me if I have the right idea, or even how I would implement the map properly?

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• Could this be considered a well-written class (am I using OOP correctly)?

  - by Ben Dauphinee

  I have been learning OOP principals on my own for a while, and taken a few cracks at writing classes. What I really need to know now is if I am actually using what I have learned correctly, or if I could improve as far as OOP is concerned. I have chopped a massive portion of code out of a class that I have been working on for a while now, and pasted it here. To all you skilled and knowledgeable programmers here I ask: Am I doing it wrong? class acl extends genericAPI{ // -- Copied from genericAPI class protected final function sanityCheck($what, $check, $vars){ switch($check){ case 'set': if(isset($vars[$what])){return(1);}else{return(0);} break; } } // --------------------------------- protected $db = null; protected $dataQuery = null; public function __construct(Zend_Db_Adapter_Abstract $db, $config = array()){ $this->db = $db; if(!empty($config)){$this->config = $config;} } protected function _buildQuery($selectType = null, $vars = array()){ // Removed switches for simplicity sake $this->dataQuery = $this->db->select( )->from( $this->config['table_users'], array('tf' => '(CASE WHEN count(*) > 0 THEN 1 ELSE 0 END)') )->where( $this->config['uidcol'] . ' = ?', $vars['uid'] ); } protected function _sanityRun_acl($sanitycheck, &$vars){ switch($sanitycheck){ case 'uid_set': if(!$this->sanityCheck('uid', 'set', $vars)){ throw new Exception(ERR_ACL_NOUID); } $vars['uid'] = settype($vars['uid'], 'integer'); break; } } private function user($action = null, $vars = array()){ switch($action){ case 'exists': $this->_sanityRun_acl('uid_set', $vars); $this->_buildQuery('user_exists_idcheck', $vars); return($this->db->fetchOne($this->dataQuery->__toString())); break; } } public function user_exists($uid){ return($this->user('exists', array('uid' => $uid))); } } $return = $acl_test->user_exists(1);

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• Changing file permissions in kernel.

  - by Mehrdad

  I am writing kernel module(C in Linux) and I want to change the permission of the other files in it. any solution? since I am in kernel I can't use chmod syscall and ... thanks for your help This is my Makefile: > obj-m += ca.o > > all: > make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules > > clean: > make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean And this is my Code: > #include <linux/string.h> > #include <linux/mm.h> > /* Snip, tons of includes (all of them :))*/ > #include <linux/delay.h> .... int procfile_write(struct file *file, > const char *buffer, unsigned long > count, > void *data) { ... sys_chmod(path, per); ... } ... When Making it gives a warning: WARNING: "sys_chmod" [file] undefiened and when loading the module with "sudo insmod" it gives this error: Unknown sybol in module it seems that this error happens especialy in kernel modules. any idea? again thanks!

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• What makes my code DDD (domain-driven design) qualified?

  - by oykuo

  Hi All, I'm new to DDD and am thinking about using this design technique in my project. However, what strikes me about DDD is that how basic the idea is. Unlike other design techniques such as MVC and TDD, it doesn't seems to contain any ground breaking ideas. For example, I'm sure some of you will have the same feeling that the idea of root aggregates and repositories are nothing new because when you are was writing MVC web applications you have to have one single master object (i.e. the root aggregate) that contain other minor objects (i.e. value objects and entities) in the model layer in order to send data to a strongly typed view. To me, the only new idea in DDD is probably the "Smart" entities (i.e. you are supposed to have business rules on root aggregates) Separation between value object, root aggregate and entities. Can anyone tell me if I have missed out anything here? If that's all there is to DDD, if I update one of my existing MVC application with the above 2 new ideas, can I claim it's an TDD, MVC and DDD applcation?

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• How can I differentiate two different touches on a layer ?

  - by srikanth rongali

  I am writing an app in cocos2d. I hava a sprite and a text in my scene. I have written two separate classes for sprite and text. And I added both of them to another class. In sprite class I have written - (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event And in text class I have written -(void) registerWithTouchDispatcher { [[CCTouchDispatcher sharedDispatcher]addTargetedDelegate:self priority:0 swallowsTouches:YES]; } -(BOOL) ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event { return YES; } -(void) ccTouchEnded:(UITouch *)touch withEvent:(UIEvent *)event { NSLog(@"Recognized tOuches in Instructions");// CGSize windowSize = [[CCDirector sharedDirector] winSize]; CCNode *node = [self getChildByTag:kTagNode]; [node setPosition: ccp(text1.contentSize.width/2,text1.contentSize.height/2 - windowSize.height)]; } -(void) ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event { CGPoint touchLocation = [touch locationInView: [touch view]]; CGPoint prevLocation = [touch previousLocationInView: [touch view]]; touchLocation = [[CCDirector sharedDirector] convertToGL: touchLocation]; prevLocation = [[CCDirector sharedDirector] convertToGL: prevLocation]; CGPoint diff = ccpSub(touchLocation,prevLocation); CCNode *node = [self getChildByTag:kTagNode]; CGPoint currentPos = [node position]; [node setPosition: ccpAdd(currentPos, diff)]; } But, only touches in the text are recognized and touch of sprite is not recognized ? How can I differentiate the two touches.

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• Make a PHP GET request from a PHP script and exit

  - by Abs

  Hello all, Is there something simpler than the following. I am trying to make a GET request to a PHP script and then exit the current script. I think this is a job for CURL but is there something simpler as I don't want to really worry about enabling the CURL php extension? In addition, will the below start the PHP script and then just come back and not wait for it to finish? //set GET variables $url = 'http://domain.com/get-post.php'; $fields = array( 'lname'=>urlencode($last_name), 'fname'=>urlencode($first_name) ); //url-ify the data for the GET foreach($fields as $key=>$value) { $fields_string .= $key.'='.$value.'&'; } rtrim($fields_string,'&'); //open connection $ch = curl_init(); //set the url, number of POST vars, POST data curl_setopt($ch,CURLOPT_URL,$url); curl_setopt($ch,CURLOPT_GET,count($fields)); curl_setopt($ch,CURLOPT_GETFIELDS,$fields_string); //execute GET $result = curl_exec($ch); //close connection curl_close($ch); I want to run the other script which contains functions when a condition is met so a simple include won't work as the if condition wraps around the functions, right? Please note, I am on windows machine and the code I am writing will only be used on a Windows OS. Thanks all for any help and advice

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• autoreload webpage on new release

  - by user3726562

  I have a website in PHP which is completely ajax-based. There is an index.php, but a part from it, all the other page are never rendered directly into the browser. Instead, all the post and get request are done tfrom javascript through ajax. So basically, if you go to /contact.php you will not see anything. All the pages are rendered inside index.php. So, there are a lot of people that use this page that are not very good in using the web. Asking them to "refresh" the page makes them to wonder what we are talking about. Unfortunately. The biggest issue happens when we do a new release. Especially the javascript code (but not only) can be the old one in a client's webpage as they maybe havent refreshed the page for some week (lol). S I do an svn-update and the new code is on the server. I just refresh my page and see the new features. However, the poor guys that dont really know how to make a refresh, will not see anything. I have added a big button on the page with the text "refresh". Which makes a location.reload. Hopefully this can help a few of them. But my question is: how to "force" the browser to reload itself when a new svn-version has been released? Hopefully in a simple way, without needing some node.js, javascript timer or stuff like that. It is also quite important to not refresh the page when the user is doing something with the page (maybe writing a mail in the UI, and then suddenly the page get refreshed: not so good).

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• C++: Vector of objects vs. vector of pointers to new objects?

  - by metamemetics

  Hello, I am seeking to improve my C++ skills by writing a sample software renderer. It takes objects consisting of points in a 3d space and maps them to a 2d viewport and draws circles of varying size for each point in view. Which is better: class World{ vector<ObjectBaseClass> object_list; public: void generate(){ object_list.clear(); object_list.push_back(DerivedClass1()); object_list.push_back(DerivedClass2()); or... class World{ vector<ObjectBaseClass*> object_list; public: void generate(){ object_list.clear(); object_list.push_back(new DerivedClass1()); object_list.push_back(new DerivedClass2()); ?? Would be using pointers in the 2nd example to create new objects defeat the point of using vectors, because vectors automatically call the DerivedClass destructors in the first example but not in the 2nd? Are pointers to new objects necessary when using vectors because they handle memory management themselves as long as you use their access methods? Now let's say I have another method in world: void drawfrom(Viewport& view){ for (unsigned int i=0;i<object_list.size();++i){ object_list.at(i).draw(view); } } When called this will run the draw method for every object in the world list. Let's say I want derived classes to be able to have their own versions of draw(). Would the list need to be of pointers then in order to use the method selector (-) ?

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• How do I parse data received in a memorystream?

  - by Kerberos42

  I'm new to using sockets. I have a very basic client that sends a request, and waits for a response. The response is one stream, but has two parts. The first part is prefixed with ANS and is a set of key/value pairs in this form: KEY:Value with each pair on a separate line. The second part of the response is prefixed by RCT and this is pre-formatted text that needs to be send directly to a printer. So what would be the best way to extract both parts of the response, and in the first part, get each Key:Value pair. I might not even need them all, but I have to look at each one to see what the values are then decide what to do with it. I'm currently writing the response out to a textbox just to understand what its doing, but now I need to actually do something with the data. Here's a data sample, as it is received: ANS Result: Data Received RCPRES:Q[81] TML:123 OPP: MRR:000000999999 <several dozen more KEY:Value pairs> RCTNov 05 2013 04:03 pm Trans# 123456 <pre-formatted text>

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• Doesn't this defeat the whole purpose of having read-only properties?

  - by flockofcode

  I know how to use properties and I understand that they implicitly call underlying get and set accessors, depending on whether we are writing to or reading from a property. static void Main(string[] args) { A a = new A(); (a.b).i = 100; } class A { private B _b = new B(); public B b { get { return _b; } } } class B { public int i; } What code (a.b).i = 100; essentially does is that first property’s get accessor returns a reference to an object _b, and once we have this reference, we are able to access _b’s members and change their values. Thus, in our example, having read only property only prevents outside code from changing the value of a reference variable _b, but it doesn’t prevent outside code from accessing _b’s members. So it seems that property can only detect whether we are trying to read from or write to a variable ( in our case variable _b ) located on the stack, while it’s not able to detect whether we’re trying to also write to members of an object to which the variable on the stack ( assuming this variable is of reference type ) points to. a) But doesn’t that defeat the whole purpose of having read-only properties? Wouldn’t it be more effective if properties had the ability to also detect whether we’re trying to access members of an object returned by get accessor( assuming backing field is of a reference type )? thank you

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• Creating a new variable in C from only part of an existing u_char

  - by Alex Kloss

  I'm writing some C code to parse IEEE 802.11 frames, but I'm stuck trying to create a new variable whose length depends on the size of the frame itself. Here's the code I currently have: int frame_body_len = pkt_hdr->len - radio_hdr->len - wifi_hdr_len - 4; u_char *frame_body = (u_char *) (packet + radio_hdr->len + wifi_hdr_len); Basically, the frame consists of a header, a body, and a checksum at the end. I can calculate the length of the frame body by taking the length of the packet and subtracting the length of the two headers that appear before it (radio_hdr->len and wifi_hdr_len respectively), plus 4 bytes at the end for the checksum. However, how can I create the frame_body variable without the trailing checksum? Right now, I'm initializing it with the contents of the packet starting at the position after the two headers, but is there some way to start at that position and end 4 bytes before the end of packet? packet is a pointer to a u_char, if it helps. I'm a new C programmer, so any and all advice about my code you can give me would be much appreciated. Thanks!

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• php memory how much is too much

  - by Rob

  I'm currently re-writing my site using my own framework (it's very simple and does exactly what I need, i've no need for something like Zend or Cake PHP). I've done alot of work in making sure everything is cached properly, caching pages in files so avoid sql queries and generally limiting the number of sql queries. Overall it looks like it's very speedy. The average time taken for the front page (taken over 100 times) is 0.046152 microseconds. But one thing i'm not sure about is whether i've done enough to reduce php memory usage. The only time i've ever encountered problems with it is when uploading large files. Using memory_get_peak_usage(TRUE), which I THINK returns the highest amount of memory used whilst the script has been running, the average (taken over 100 times) is 1572864 bytes. Is that good? I realise you don't know what it is i'm doing (it's rather simple, get the 10 latest articles, the comment count for each, get the user controls, popular tags in the sidebar etc). But would you be at all worried with a script using that sort of memory getting hit 50,000 times a day? Or once every second at peak times? I realise that this is a very open ended question. Hopefully you can understand that it's a bit of a stab in the dark and i'm really just looking for some re-assurance that it's not going to die horribly come re-launch day.

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