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• Is there a way to cause a new C++ class instance to fail, if certain conditions in the contructor ar

  - by Jim Fell

  As I understand it, when a new class is instantiated in C++, a pointer to the new class is returned, or NULL, if there is insufficient memory. I am writing a class that initializes a linked list in the constructor. If there is an error while initializing the list, I would like the class instantiator to return NULL. For example: MyClass * pRags = new MyClass; If the linked list in the MyClass constructor fails to initialize properly, I would like pRags to equal NULL. I know that I can use flags and additional checks to do this, but I would like to avoid that, if possible. Does anyone know of a way to do this? Thanks.

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• What happens if the first part of an if-structure is false?

  - by djerry

  Hey guys, I was wondering what happens when a program processes an if-structure with multiple conditions. I have an idea, but i'm not sure about it. I'll give an example : List<string> myTestList = null; if (myTestList != null && myTestList.Count > 0) { //process } The list is null. When processing the if, will it go from left to right exiting the if as soon as one condition is false? I've tried it and seems to throw no errors, so i assume the above explains it, but i'm not sure. Thanks in advance.

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• GetValue on static field inside nested classes.

  - by Sir Gallahad

  Hi... I have the following class declared. I need to retreive the class structure and the static values without instanciate it. public MyClass() { public static string field = "Value"; public nestedClass() { public static string nestedField = "NestedValue"; } } I've successfuly used GetFields and GetNestedType to recover the class structure and GetValue(null) works fine on field, but not on nestedField. Let me sample: var fi = typeof(MyClass).GetField("field", BindingFlags.Public | BindingFlags.Static); var nt = typeof(MyClass).GetNestedType("nestedClass", BindingFlags.Public); var nfi = nt.GetField("nestedField", BindingFlags.Public | BindingFlags.Static); // All the above references are detected correctly var value = fi.GetValue(null); // until here everything works fine. value == "Value" var nestedValue = nfi.GetValue(null); // this one does not work!! Anyone knows why the last line does not work and how to work around? Thanks.

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• MySQL function return more than 1 row

  - by bobobobo

  I'd like to write a MySQL stored function that returns multiple rows of data. Is this possible? It seems to be locked at 1 row -- can't even return 0 rows. For example DELIMITER // create function go() RETURNS int deterministic NO SQL BEGIN return null ; -- this doesn't return 0 rows! it returns 1 row -- return 0 ; END // DELIMITER ; Returning null from a MySQL stored proc though, doesn't return 0 rows.. it returns 1 row with the value null in it. Can I return 0, or more than 1 row from a MySQL function, how?

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• How do I stop setNeedsDisplayInRect / drawRect coalescence?

  - by No One in Particular

  When programming my app, I get to the point where I have to update two rectangles on the screen. So I call [self setNeedsDisplayInRect:rect1] and then [self setNeedsDisplayInRect:rect2]. When my drawRect method is called, the rectangle parameter is the smallest rectangle which contains both rect1 and rect2. I can handle this with no problem, but when the two rectangles are far apart, then I am updating a lot of real estate with no gain. In this case, I would just like to repaint my two small rectangles. So my question is how can I prevent the underlying system from coalescing my two calls into one?

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• Help with running crontab from root

  - by user242065

  Im using OSX and having trouble getting a cron job to run. I type the following: $ sudo -i $ crontab -e I then enter: * * * * * root ifconfig en0 down > /dev/null 0 19 * * * root ifconfig en0 down > /dev/null 0 7 * * * root ifconfig en0 up > /dev/null and no success, the first line is for testing. I want it to shut off my internet. The next two lines I plan to leave in, once I get this working. If I type this in to the terminal the internet goes off ifconfig en0 down Why is my cron job not shutting down the internet? FYI: This is a follow up question from http://stackoverflow.com/questions/3027362/how-can-i-write-a-cron-job-that-will-block-my-internet-from-7pm-to-7am-so-i-can most of the comments there are people making fun of me. And a few attempts to solve the problem with out cron jobs.

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• Generate Permutations of a List

  - by Eric Mercer

  I'm writing a function that takes a list and returns a list of permutations of the argument. I know how to do it by using a function that removes an element and then recursively use that function to generate all permutations. I now have a problem where I want to use the following function: (define (insert-everywhere item lst) (define (helper item L1 L2) (if (null? L2) (cons (append L1 (cons item '())) '()) (cons (append L1 (cons item L2)) (helper item (append L1 (cons (car L2) '())) (cdr L2))))) (helper item '() lst)) This function will insert the item into every possible location of the list, like the following: (insert-everywhere 1 '(a b)) will get: '((1 a b) (a 1 b) (a b 1)) How would I use this function to get all permutations of a list? I now have: (define (permutations lst) (if (null? lst) '() (insert-helper (car lst) (permutations (cdr lst))))) (define (insert-helper item lst) (cond ((null? lst) '()) (else (append (insert-everywhere item (car lst)) (insert-helper item (cdr lst)))))) but doing (permutations '(1 2 3)) just returns the empty list '().

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• Converting a C# code to F#??

  - by Brendon

  Hello all I am just a beginner in programing i wish covert some code from C# to F#, I have encotered this code: float[] v1=new float[10]; ... //Enqueue the Execute command. Queue.Execute(kernelVecSum, null, **new long[] { v1.Length }**, null, null); I have previously ask how to convert the v1 object, I think i know how, But how do i use the function call especially the "new long[] { v1.Length }" part of the function argument, what does "new long[] { v1.Length }" mean?? I have created v1 like this "let v1 = [| for i in 1.0 .. 10.0 -> 2.0 * i |]" Is it correct?? or should i use v1 like this "let v1 = ref [| for i in 1.0 .. 10.0 -> 2.0 * i |]" ???

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• Should I Use GUID or IDENTITY as Thread Number?

  - by user311509

  offerID is the thread # which represents the thread posted. I see in forums posts are represented by random numbers. Is this achieved by IDENTITY? If not, please advice. nvarchar(max) will carry all kind of texts along with HTML tags. CREATE TABLE Offer ( offerID int IDENTITY (4382,15) PRIMARY KEY, memberID int NOT NULL REFERENCES Member(memberID), title nvarchar(200) NOT NULL, thread nvarchar(max) NOT NULL, . . . );

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• Assigning two strings together getting Access Read Violation

  - by Jay Bell

  I am trying to pass a string to a class mutator and set the private member to that string here is the code that is sending the string void parseTradePairs(Exchange::Currency *curr, std::string *response, int begin, int exit) { int start; int end; string temp; string dataResponse; CURL *tempCurl; initializeCurl(tempCurl); int location = response->find("marketid", begin); if(location <= exit) { start = location + 11; begin = response->find("label", start); end = begin - start - 3; findStrings(start, end, temp, response); getMarketInfo(tempCurl, temp, dataResponse); curr->_coin->setExch(temp); // here is the line of code that is sending the string dataResponse >> *(curr->_coin); curr->_next = new Exchange::Currency(curr, curr->_position + 1); parseTradePairs(curr->_next, response, begin, exit); } } and here is the mutator within the coin class that is receiving the string and assigning it to _exch void Coin::setExch(string exch) { _exch = exch; } I have stepped through it and made sure that exch has the string in it. "105" but soon as it hits _exch = exch; I get the reading violation. I tried passing as pointer as well. I do not believe it should go out of scope. and the string variable in the class is initialized to zero in the default constructor but again that should matter unless I am trying to read from it instead of writing to it. /* defualt constructor */ Coin::Coin() { _id = ""; _label = ""; _code= ""; _name = ""; _marketCoin = ""; _volume = 0; _last = 0; _exch = ""; } Exchange::Exchange(std::string str) { _exch = str; _currencies = new Currency; std::string pair; std::string response; CURL *curl; initializeCurl(curl); getTradePairs(curl, response); int exit = response.find_last_of("marketid"); parseTradePairs(_currencies, &response, 0, exit); } int main(void) { CURL *curl; string str; string id; Coin coin1; initializeCurl(curl); Exchange ex("cryptsy"); curl_easy_cleanup(curl); system("pause"); return 0; } class Exchange { public: typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() : _next(NULL), _prev(NULL), _position(0) {} Coin *_coin; Currency *_next; Currency *_prev; int _position; }; /* constructor and destructor */ Exchange(); Exchange(std::string str); ~Exchange(); /* Assignment operator */ Exchange& operator =(const Exchange& copyExchange); /* Parse Cryptsy Pairs */ friend void parseTradePairs(Currency *curr, std::string *response, int begin, int exit); private: std::string _exch; Currency *_currencies; }; here is what i changed it to to fix it. typedef struct Currency { Currency(Coin *coin, Currency *next, Currency *prev, int position) : _coin(coin), _next(next), _prev(prev), _position(position) {} Currency(Currency *prev, int position) : _prev(prev), _position(position), _next(NULL), _coin(&Coin()){} Currency() { _next = NULL; _prev = NULL; _position = 0; _coin = new Coin(); } Coin *_coin; Currency *_next; Currency *_prev; int _position; };

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• How to update content of one ArrayController from the selected value of another ArrayController in Ember.js

  - by CodeHugger

  I have the following problem in ember.js. A child controller depends on a selected value in a parent controller in order to determine its content. In the database a child has a parent_id reference. App.parentsController = Em.ArrayController.create({ content: [], selected: null }); App.sonsController = Em.ArrayController.create({ // the value of content depends on the id of // the selected item in the parentsController content: [], selected: null }); App.daughtersController = Em.ArrayController.create({ // the value of content depends on the id of // the selected item in the parentsController content: [], selected: null }); I would prefer to solve this without the parentsController having to know anything about the other controllers. This should be possible with observers, bindings or even through calculations but I have no clue where to start. Any help would be well appreciated.

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• Oracle spatial search within distance

  - by KA_lin

  I have the following table Cities: ID(int),City(char),latitude(float),longitude(float). Now based on a user`s longitude(ex:44.8) and latitude(ex:46.3) I want to search for all the cities near him within 100 miles/KM. I have found some examples but don`t know how to adapt them to my case select * from GEO.Cities a where SDO_WITHIN_DISTANCE([I don`t know], MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(44.8,46.3, NULL) ,NULL, NULL), 'distance = 1000') = 'TRUE'; Any help would be appreciated. P.S: If it is possible to have the distance and to be sorted P.P.S: I want to do it in this way due to performance issues, I have done this in this way http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL but it takes too long...

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• Allocating memory for a array to char pointer

  - by nunos

  The following piece of code gives a segmentation fault when allocating memory for the last arg. What am I doing wrong? Thanks. int n_args = 0, i = 0; while (line[i] != '\0') { if (isspace(line[i++])) n_args++; } for (i = 0; i < n_args; i++) command = malloc (n_args * sizeof(char*)); char* arg = NULL; arg = strtok(line, " \n"); while (arg != NULL) { arg = strtok(NULL, " \n"); command[i] = malloc ( (strlen(arg)+1) * sizeof(char) ); strcpy(command[i], arg); i++; } Thanks.

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• C# Constructor Problem When Using Generics

  - by Jimbo

  Please see an example of my code below: public class ScrollableCheckboxList { public List<ScrollableCheckboxItem> listitems; public void ScrollableCheckboxList<TModel>(IEnumerable<TModel> items, string valueField, string textField, string titleField) where TModel : class { listitems = new List<ScrollableCheckboxItem>(); foreach (TModel item in items) { Type t = typeof(TModel); PropertyInfo[] props = new [] { t.GetProperty(textField), t.GetProperty(valueField), t.GetProperty(titleField) }; listitems.Add(new ScrollableCheckboxItem { text = props[0].GetValue(item, null).ToString(), value = props[1].GetValue(item, null).ToString(), title = props[2].GetValue(item, null).ToString() }); } } } The code produces the following error: 'ScrollableCheckboxList': member names cannot be the same as their enclosing type This clearly means that there is a method in the class that has the same name as the class, but usually insinuates that the method is trying to return something (which is not allowed) In my case, all I have done is declare a constructor - why would this be a problem?

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• Importing libraries in eclipse programmatically

  - by Krt_Malta

  Hi, Is there a way I could put a library (Jar file) into an Eclipse project programatically? Up to now I've managed to do an external reference to it programatically using IPath path = new Path("C:\\Hello\\jtwitter.jar"); libraries.add(JavaCore.newLibraryEntry(path, null, null)); //add libs to project class path try { javaProject.setRawClasspath(libraries.toArray(new IClasspathEntry[libraries.size()]), null); } catch (JavaModelException e1) { e1.printStackTrace(); } } however I'd like to copy the jtwitter file to the project folder programatically so I could reference it as jtwitter.jar only. Can this be done please? Thanks a lot and regards, Krt_Malta

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• Double use of variables?

  - by Vaccano

  I have read that a variable should never do more than one thing. Overloading a variable to do more than one thing is bad. Because of that I end up writing code like this: (With the customerFound variable) bool customerFound = false; Customer foundCustomer = null; if (currentCustomer.IsLoaded) { if (customerIDToFind = currentCustomer.ID) { foundCustomer = currentCustomer; customerFound = true; } } else { foreach (Customer customer in allCustomers) { if (customerIDToFind = customer.ID) { foundCustomer = customer; customerFound = true; } } } if (customerFound) { // Do something } But deep down inside, I sometimes want to write my code like this: (Without the foundCustomer variable) Customer foundCustomer = null; if (currentCustomer.IsLoaded) { if (customerIDToFind = currentCustomer.ID) { foundCustomer = currentCustomer; } } else { foreach (Customer customer in allCustomers) { if (customerIDToFind = customer.ID) { foundCustomer = customer; } } } if (foundCustomer != null) { // Do something } Does this secret desires make me an evil programmer? (i.e. is the second case really bad coding practice?)

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• Create empty C# event handlers automatically

  - by TomA

  It is not possible to fire an event in C# that has no handlers attached to it. So before each call it is necessary to check if the event is null. if ( MyEvent != null ) { MyEvent( param1, param2 ); } I would like to keep my code as clean as possible and get rid of those null checks. I don't think it will affect performance very much, at least not in my case. MyEvent( param1, param2 ); Right now I solve this by adding an empty inline handler to each event manually. This is error prone, since I need to remember to do that etc. void Initialize() { MyEvent += new MyEvent( (p1,p2) => { } ); } Is there a way to generate empty handlers for all events of a given class automatically using reflection and some CLR magic?

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• How to detect padding on an integer and treat it as a string?

  - by Sirber

  I have this function to prepare variable to be used in a SQL query: function sqlize($mInput) { if (!isset($mInput)) $mInput = "null"; elseif (strtolower($mInput) == "null") { } elseif (is_numeric($mInput)) { } elseif (is_string($mInput)) { $mInput = trim($mInput); $mInput = addslashes($mInput); $mInput = '"' . $mInput . '"'; } else $mInput = "null"; return $mInput; } I have a string "0004", which is going in a "varchar field", is cought by is_numeric, and is saved as "4" and not "0004". Is there a way to detect the padding and process it as a string? Thank you!

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• Filter condition not working properly on list (C#3.0)

  - by Newbie

  I have a datatable that has many NULL or " " strings. Next I am type casting the DataTable to a list . Now if I want to filter those conditions on this list and get the resultant value(without NULL or String.Empty or " " records) what should I do? My code DataTableExtensions.AsEnumerable(dt).ToList().ForEach(i => { if (i[0] != null) { if ((i[0].ToString() != string.Empty)|| (i[0].ToString() != " ")) { list = dt.AsEnumerable().ToList(); } } }); But I am getting all the records. It is not getting filtered. Using C#3.0 Please help Thanks

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• Problem with pointer copy in C

  - by Stefano Salati

  I radically re-edited the question to explain better my application, as the xample I made up wasn't correct in many ways as you pointed out: I have one pointer to char and I want to copy it to another pointer and then add a NULL character at the end (in my real application, the first string is a const, so I cannot jsut modify it, that's why I need to copy it). I have this function, "MLSLSerialWriteBurst" which I have to fill with some code adapt to my microcontroller. tMLError MLSLSerialWriteBurst( unsigned char slaveAddr, unsigned char registerAddr, unsigned short length, const unsigned char *data ) { unsigned char *tmp_data; tmp_data = data; *(tmp_data+length) = NULL; // this function takes a tmp_data which is a char* terminated with a NULL character ('\0') if(EEPageWrite2(slaveAddr,registerAddr,tmp_data)==0) return ML_SUCCESS; else return ML_ERROR; } I see there's a problem here: tha fact that I do not initialize tmp_data, but I cannot know it's length.

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• embedded dev. question - how to break free from a faulty serial port opening?

  - by user347266

  Under WindowsCE, C++ project, I'm trying to work with devices connected via both "real" serial ports and/or serial-to-usb wrappers ("virtual" serial ports); my problem is - when I try to open the port, if something goes wrong, the function never returns and the system goes into some non-responsive state and has to be eventually rebooted. I need to open the ports from the main thread. The question is - how can I make it happen in a controlled way?? this is the opening code snippet: std::ostringstream device_name; device_name << "\\.\COM" << port; m_port = ::CreateFile(device_name.str().c_str(), GENERIC_READ | GENERIC_WRITE, 0, // exclusive access NULL, // no security OPEN_EXISTING, FILE_FLAG_OVERLAPPED, // overlapped I/O NULL); // null template any suggestions would be greatly appreciated thanks!

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• how to dynamically recolor a CGGradientRef

  - by saintmac

  I have three CGGradientRef's that I need to be able to dynamically recolor. When I Initialise the CGGradientRef's the first time I get the expected result, but every time I attempt to change the colors nothing happens. Why? gradient is an instance variable ins a subclass of CALayer: @interface GradientLayer : CALayer { CGGradientRef gradient; //other stuff } @end Code: if (gradient != NULL) { CGGradientRelease(gradient); gradient = NULL; } RGBA color[360]; //set up array CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB(); gradient = CGGradientCreateWithColorComponents ( rgb, color, NULL, sizeof (color) / sizeof (color[0]) ); CGColorSpaceRelease(rgb); [self setNeedsDisplay];

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• Help me to break array

  - by Wazzy

  Please Help me getting only emails from this array Mentioning array not in code tags is intentional-Sorry for that array(16) { [0]=> string(273) ""guid":"","contactId":"44","contactName":"_, atri","email":"[email protected]","emaillink":"http:\/\/mrd.mail.yahoo.com\/compose?To=atri_megrez%40yahoo.com","isConnection":false,"connection":"","displayImg":null,"msgrID":"atri_megrez","msgrStatus":"","isMsgrBuddy":122}," [1]=> string(260) ""guid":"","contactId":"100","contactName":"afrin","email":"[email protected]","emaillink":"http:\/\/mrd.mail.yahoo.com\/compose?To=fida_cuty123%40yahoo.com","isConnection":false,"connection":"","displayImg":null,"msgrID":"","msgrStatus":"","isMsgrBuddy":false}," [2]=> string(258) ""guid":"","contactId":"101","contactName":"afrin","email":"[email protected]","emaillink":"http:\/\/mrd.mail.yahoo.com\/compose?To=waliyani%40yahoo.com","isConnection":false,"connection":"","displayImg":null,"msgrID":"","msgrStatus":"","isMsgrBuddy":false}," }

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• retrieve value from db in php

  - by wangdoo

  I have a db in which 1 column value will be always null.I want it to pass to next page but it is passing all values of other column except this null value column. This is my code $row=mysql_query("SELECT * FROM `thirdpartycategorymaster` WHERE ISNULL(`delete`)"); while($row1=mysql_fetch_array($row)) { <td><b><a href="catdel.php?head1=<?php echo $row1['ThirdPartyCategoryName'] . '&&msg1=' . $row1['ThirdPartyCategoryID'] . '&&ctdel=' . $row1['delete']; ?> ">Delete</a></b></td> This my db table ThirdPartyCategoryID ThirdPartyCategoryName delete 29 ecommerce NULL

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• MySQL Query, Date Range From "Blacklist"

  - by erbaker

  I have 2 databases. One is properties and the other is dates. In dates I have associated the land_id and a date (In YYYYMMDD format) which means that the date is not available. I need to formulate a query that a user can specify a start and end date, and then choose a property for which dates are available (not in the date database). How do airline and hotel websites do this kind of logic? I was thinking about taking the date range and picking all days in between and doing a query where the dates do not match and ordering it by number of results, but I can see how that could easily turn into an intense query. CREATE TABLE IF NOT EXISTS `dates` ( `id` int(11) NOT NULL AUTO_INCREMENT, `land_id` int(11) NOT NULL, `date` varchar(255) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=44 ; -- -- Dumping data for table `dates` -- INSERT INTO `dates` (`id`, `land_id`, `date`) VALUES (43, 1, '20100526'), (39, 1, '20100522'), (40, 1, '20100523'), (41, 1, '20100521'), (42, 1, '20100525');

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