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• Should I create a unique clustered index, or non-unique clustered index on this SQL 2005 table?

  - by Bremer

  I have a table storing millions of rows. It looks something like this: Table_Docs ID, Bigint (Identity col) OutputFileID, int Sequence, int …(many other fields) We find ourselves in a situation where the developer who designed it made the OutputFileID the clustered index. It is not unique. There can be thousands of records with this ID. It has no benefit to any processes using this table, so we plan to remove it. The question, is what to change it to… I have two candidates, the ID identity column is a natural choice. However, we have a process which does a lot of update commands on this table, and it uses the Sequence to do so. The Sequence is non-unique. Most records only contain one, but about 20% can have two or more records with the same Sequence. The INSERT app is a VB6 piece of crud throwing thousands insert commands at the table. The Inserted values are never in any particular order. So the Sequence of one insert may be 12345, and the next could be 12245. I know that this could cause SQL to move a lot of data to keep the clustered index in order. However, the Sequence of the inserts are generally close to being in order. All inserts would take place at the end of the clustered table. Eg: I have 5 million records with Sequence spanning 1 to 5 million. The INSERT app will be inserting sequence’s at the end of that range at any given time. Reordering of the data should be minimal (tens of thousands of records at most). Now, the UPDATE app is our .NET star. It does all UPDATES on the Sequence column. “Update Table_Docs Set Feild1=This, Field2=That…WHERE Sequence =12345” – hundreds of thousands of these a day. The UPDATES are completely and totally, random, touching all points of the table. All other processes are simply doing SELECT’s on this (Web pages). Regular indexes cover those. So my question is, what’s better….a unique clustered index on the ID column, benefiting the INSERT app, or a non-unique clustered index on the Sequence, benefiting the UPDATE app?

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• C++ HW - defining classes - objects that have objects of other class problem in header file (out of

  - by kitfuntastik

  This is my first time with much of this code. With this instancepool.h file below I get errors saying I can't use vector (line 14) or have instance& as a return type (line 20). It seems it can't use the instance objects despite the fact that I have included them. #ifndef _INSTANCEPOOL_H #define _INSTANCEPOOL_H #include "instance.h" #include <iostream> #include <string> #include <vector> #include <stdlib.h> using namespace std; class InstancePool { private: unsigned instances;//total number of instance objects vector<instance> ipp;//the collection of instance objects, held in a vector public: InstancePool();//Default constructor. Creates an InstancePool object that contains no Instance objects InstancePool(const InstancePool& original);//Copy constructor. After copying, changes to original should not affect the copy that was created. ~InstancePool();//Destructor unsigned getNumberOfInstances() const;//Returns the number of Instance objects the the InstancePool contains. const instance& operator[](unsigned index) const; InstancePool& operator=(const InstancePool& right);//Overloading the assignment operator for InstancePool. friend istream& operator>>(istream& in, InstancePool& ip);//Overloading of the >> operator. friend ostream& operator<<(ostream& out, const InstancePool& ip);//Overloading of the << operator. }; #endif Here is the instance.h : #ifndef _INSTANCE_H #define _INSTANCE_H ///////////////////////////////#include "instancepool.h" #include <iostream> #include <string> #include <stdlib.h> using namespace std; class Instance { private: string filenamee; bool categoryy; unsigned featuress; unsigned* featureIDD; unsigned* frequencyy; string* featuree; public: Instance (unsigned features = 0);//default constructor unsigned getNumberOfFeatures() const; //Returns the number of the keywords that the calling Instance object can store. Instance(const Instance& original);//Copy constructor. After copying, changes to the original should not affect the copy that was created. ~Instance() { delete []featureIDD; delete []frequencyy; delete []featuree;}//Destructor. void setCategory(bool category){categoryy = category;}//Sets the category of the message. Spam messages are represented with true and and legit messages with false.//easy bool getCategory() const;//Returns the category of the message. void setFileName(const string& filename){filenamee = filename;}//Stores the name of the file (i.e. “spam/spamsga1.txt”, like in 1st assignment) in which the message was initially stored.//const string& trick? string getFileName() const;//Returns the name of the file in which the message was initially stored. void setFeature(unsigned i, const string& feature, unsigned featureID,unsigned frequency) {//i for array positions featuree[i] = feature; featureIDD[i] = featureID; frequencyy[i] = frequency; } string getFeature(unsigned i) const;//Returns the keyword which is located in the ith position.//const string unsigned getFeatureID(unsigned i) const;//Returns the code of the keyword which is located in the ith position. unsigned getFrequency(unsigned i) const;//Returns the frequency Instance& operator=(const Instance& right);//Overloading of the assignment operator for Instance. friend ostream& operator<<(ostream& out, const Instance& inst);//Overloading of the << operator for Instance. friend istream& operator>>(istream& in, Instance& inst);//Overloading of the >> operator for Instance. }; #endif Also, if it is helpful here is instance.cpp: // Here we implement the functions of the class apart from the inline ones #include "instance.h" #include <iostream> #include <string> #include <stdlib.h> using namespace std; Instance::Instance(unsigned features) { //Constructor that can be used as the default constructor. featuress = features; if (features == 0) return; featuree = new string[featuress]; // Dynamic memory allocation. featureIDD = new unsigned[featuress]; frequencyy = new unsigned[featuress]; return; } unsigned Instance::getNumberOfFeatures() const {//Returns the number of the keywords that the calling Instance object can store. return featuress;} Instance::Instance(const Instance& original) {//Copy constructor. filenamee = original.filenamee; categoryy = original.categoryy; featuress = original.featuress; featuree = new string[featuress]; for(unsigned i = 0; i < featuress; i++) { featuree[i] = original.featuree[i]; } featureIDD = new unsigned[featuress]; for(unsigned i = 0; i < featuress; i++) { featureIDD[i] = original.featureIDD[i]; } frequencyy = new unsigned[featuress]; for(unsigned i = 0; i < featuress; i++) { frequencyy[i] = original.frequencyy[i];} } bool Instance::getCategory() const { //Returns the category of the message. return categoryy;} string Instance::getFileName() const { //Returns the name of the file in which the message was initially stored. return filenamee;} string Instance::getFeature(unsigned i) const { //Returns the keyword which is located in the ith position.//const string return featuree[i];} unsigned Instance::getFeatureID(unsigned i) const { //Returns the code of the keyword which is located in the ith position. return featureIDD[i];} unsigned Instance::getFrequency(unsigned i) const { //Returns the frequency return frequencyy[i];} Instance& Instance::operator=(const Instance& right) { //Overloading of the assignment operator for Instance. if(this == &right) return *this; delete []featureIDD; delete []frequencyy; delete []featuree; filenamee = right.filenamee; categoryy = right.categoryy; featuress = right.featuress; featureIDD = new unsigned[featuress]; frequencyy = new unsigned[featuress]; featuree = new string[featuress]; for(unsigned i = 0; i < featuress; i++) { featureIDD[i] = right.featureIDD[i]; } for(unsigned i = 0; i < featuress; i++) { frequencyy[i] = right.frequencyy[i]; } for(unsigned i = 0; i < featuress; i++) { featuree[i] = right.featuree[i]; } return *this; } ostream& operator<<(ostream& out, const Instance& inst) {//Overloading of the << operator for Instance. out << endl << "<message file=" << '"' << inst.filenamee << '"' << " category="; if (inst.categoryy == 0) out << '"' << "legit" << '"'; else out << '"' << "spam" << '"'; out << " features=" << '"' << inst.featuress << '"' << ">" <<endl; for (int i = 0; i < inst.featuress; i++) { out << "<feature id=" << '"' << inst.featureIDD[i] << '"' << " freq=" << '"' << inst.frequencyy[i] << '"' << "> " << inst.featuree[i] << " </feature>"<< endl; } out << "</message>" << endl; return out; } istream& operator>>(istream& in, Instance& inst) { //Overloading of the >> operator for Instance. string word; string numbers = ""; string filenamee2 = ""; bool categoryy2 = 0; unsigned featuress2; string featuree2; unsigned featureIDD2; unsigned frequencyy2; unsigned i; unsigned y; while(in >> word) { if (word == "<message") {//if at beginning of message in >> word;//grab filename word for (y=6; word[y]!='"'; y++) {//pull out filename from between quotes filenamee2 += word[y];} in >> word;//grab category word if (word[10] == 's') categoryy2 = 1; in >> word;//grab features word for (y=10; word[y]!='"'; y++) { numbers += word[y];} featuress2 = atoi(numbers.c_str());//convert string of numbers to integer Instance tempp2(featuress2);//make a temporary Instance object to hold values read in tempp2.setFileName(filenamee2);//set temp object to filename read in tempp2.setCategory(categoryy2); for (i=0; i<featuress2; i++) {//loop reading in feature reports for message in >> word >> word >> word;//skip two words numbers = "";//reset numbers string for (int y=4; word[y]!='"'; y++) {//grab feature ID numbers += word[y];} featureIDD2 = atoi(numbers.c_str()); in >> word;// numbers = ""; for (int y=6; word[y]!='"'; y++) {//grab frequency numbers += word[y];} frequencyy2 = atoi(numbers.c_str()); in >> word;//grab actual feature string featuree2 = word; tempp2.setFeature(i, featuree2, featureIDD2, frequencyy2); }//all done reading in and setting features in >> word;//read in last part of message : </message> inst = tempp2;//set inst (reference) to tempp2 (tempp2 will be destroyed at end of function call) return in; } } } and instancepool.cpp: // Here we implement the functions of the class apart from the inline ones #include "instancepool.h" #include "instance.h" #include <iostream> #include <string> #include <vector> #include <stdlib.h> using namespace std; InstancePool::InstancePool()//Default constructor. Creates an InstancePool object that contains no Instance objects { instances = 0; ipp.clear(); } InstancePool::~InstancePool() { ipp.clear();} InstancePool::InstancePool(const InstancePool& original) {//Copy constructor. instances = original.instances; for (int i = 0; i<instances; i++) { ipp.push_back(original.ipp[i]); } } unsigned InstancePool::getNumberOfInstances() const {//Returns the number of Instance objects the the InstancePool contains. return instances;} const Instance& InstancePool::operator[](unsigned index) const {//Overloading of the [] operator for InstancePool. return ipp[index];} InstancePool& InstancePool::operator=(const InstancePool& right) {//Overloading the assignment operator for InstancePool. if(this == &right) return *this; ipp.clear(); instances = right.instances; for(unsigned i = 0; i < instances; i++) { ipp.push_back(right.ipp[i]); } return *this; } istream& operator>>(istream& in, InstancePool& ip) {//Overloading of the >> operator. ip.ipp.clear(); string word; string numbers; int total;//int to hold total number of messages in collection while(in >> word) { if (word == "<messagecollection"){ in >> word;//reads in total number of all messages for (int y=10; word[y]!='"'; y++){ numbers = ""; numbers += word[y]; } total = atoi(numbers.c_str()); for (int x = 0; x<total; x++) {//do loop for each message in collection in >> ip.ipp[x];//use instance friend function and [] operator to fill in values and create Instance objects and read them intot he vector } } } } ostream& operator<<(ostream& out, const InstancePool& ip) {//Overloading of the << operator. out << "<messagecollection messages=" << '"' << '>' << ip.instances << '"'<< endl << endl; for (int z=0; z<ip.instances; z++) { out << ip[z];} out << endl<<"</messagecollection>\n"; } This code is currently not writing to files correctly either at least, I'm sure it has many problems. I hope my posting of so much is not too much, and any help would be very much appreciated. Thanks!

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• Having trouble doing an Update with a Linq to Sql object

  - by Pure.Krome

  Hi folks, i've got a simple linq to sql object. I grab it from the database and change a field then save. No rows have been updated. :( When I check the full Sql code that is sent over the wire, I notice that it does an update to the row, not via the primary key but on all the fields via the where clause. Is this normal? I would have thought that it would be easy to update the field(s) with the where clause linking on the Primary Key, instead of where'ing (is that a word :P) on each field. here's the code... using (MyDatabase db = new MyDatabase()) { var boardPost = (from bp in db.BoardPosts where bp.BoardPostId == boardPostId select bp).SingleOrDefault(); if (boardPost != null && boardPost.BoardPostId > 0) { boardPost.ListId = listId; // This changes the value from 0 to 'x' db.SubmitChanges(); } } and here's some sample sql.. exec sp_executesql N'UPDATE [dbo].[BoardPost] SET [ListId] = @p6 WHERE ([BoardPostId] = @p0) AND .... <snip the other fields>',N'@p0 int,@p1 int,@p2 nvarchar(9),@p3 nvarchar(10),@p4 int,@p5 datetime,@p6 int',@p0=1276,@p1=212787,@p2=N'ttreterte',@p3=N'ttreterte3',@p4=1,@p5='2009-09-25 12:32:12.7200000',@p6=72 Now, i know there's a datetime field in this update .. and when i checked the DB it's value was/is '2009-09-25 12:32:12.720' (less zero's, than above) .. so i'm not sure if that is messing up the where clause condition... but still! should it do a where clause on the PK's .. if anything .. for speed! Yes / no ? UPDATE After reading nitzmahone's reply, I then tried playing around with the optimistic concurrency on some values, and it still didn't work :( So then I started some new stuff ... with the optimistic concurrency happening, it includes a where clause on the field it's trying to update. When that happens, it doesn't work. so.. in the above sql, the where clause looks like this ... WHERE ([BoardPostId] = @p0) AND ([ListId] IS NULL) AND ... <rest snipped>) This doesn't sound right! the value in the DB is null, before i do the update. but when i add the ListId value to the where clause (or more to the point, when L2S add's it because of the optomistic concurrecy), it fails to find/match the row. wtf?

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• What is the proper way to change the UINavigationController transition effect

  - by Felipe Sabino

  I have seen lots of people asking on how to push/pop UINavigationControllers using other animations besides the default one, like flip or curl. The problem is that either the question/answer was relative old, which means the have some things like [UIView beginAnimations:] (example here) or they use two very different approaches. The first is to use UIView's transitionFromView:toView:duration:options:completion: selector before pushing the controller (with the animation flag set to NO), like the following: UIViewController *ctrl = [[UIViewController alloc] init]; [UIView transitionFromView:self.view toView:ctrl.view duration:1 options:UIViewAnimationOptionTransitionFlipFromTop completion:nil]; [self.navigationController pushViewController:ctrl animated:NO]; Another one is to use CoreAnimation explicitly with a CATransaction like the following: // remember you will have to have the QuartzCore framework added to your project for this approach and also add <QuartzCore/QuartzCore.h> to the class this code is used CATransition* transition = [CATransition animation]; transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]; transition.duration = 1.0f; transition.type = @"flip"; transition.subtype = @"fromTop"; [self.navigationController.view.layer removeAllAnimations]; [self.navigationController.view.layer addAnimation:transition forKey:kCATransition]; UIViewController *ctrl = [[UIViewController alloc] init]; [self.navigationController pushViewController:ctrl animated:NO]; There are pros and cons for both approaches. The first approach gives me a much cleaner code but restricts me from using animations like "suckEffect", "cube" and others. The second approach feels wrong just by looking at it. It starts by using undocumented transitions types (i.e. not present in the Common transition types documentation from CATransition Class Reference) which might get your app rejected from App Store (I mean might as I could not found any reference of apps being rejected because it was using this transactions, which I would also appreciate any clarification on this matter), but it gives you much more flexibility on your animations, as I can use other animation types such as "cameraIris", "rippleEffect" and so on. Regarding all that, do I really need to appeal for QuartzCore and CoreAnimation whenever I need a fancier UINavigationController transition? Is there any other way to accomplish the same effect using only UIKit? If not, will the use of string values like "flip" and "cube" instead of the pre-defined constants (kCATransitionFade, kCATransitionMoveIn, etc...) be an issue regarding my app approval in the App Store? Also, are there other pros and cons regarding both approaches that could help me deciding whether to choose each one of them?

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• multi-thread access MySQL error

  - by user188916

  I have written a simple multi-threaded C program to access MySQL,it works fine except when i add usleep() or sleep() function in each thread function. i created two pthreads in the main method, int main(){ mysql_library_init(0,NULL,NULL); printf("Hello world!\n"); init_pool(&p,100); pthread_t producer; pthread_t consumer_1; pthread_t consumer_2; pthread_create(&producer,NULL,produce_fun,NULL); pthread_create(&consumer_1,NULL,consume_fun,NULL); pthread_create(&consumer_2,NULL,consume_fun,NULL); mysql_library_end(); } void * produce_fun(void *arg){ pthread_detach(pthread_self()); //procedure while(1){ usleep(500000); printf("producer...\n"); produce(&p,cnt++); } pthread_exit(NULL); } void * consume_fun(void *arg){ pthread_detach(pthread_self()); MYSQL db; MYSQL *ptr_db=mysql_init(&db); mysql_real_connect(); //procedure while(1){ usleep(1000000); printf("consumer..."); int item=consume(&p); addRecord_d(ptr_db,"test",item); } mysql_thread_end(); pthread_exit(NULL); } void addRecord_d(MYSQL *ptr_db,const char *t_name,int item){ char query_buffer[100]; sprintf(query_buffer,"insert into %s values(0,%d)",t_name,item); //pthread_mutex_lock(&db_t_lock); int ret=mysql_query(ptr_db,query_buffer); if(ret){ fprintf(stderr,"%s%s\n","cannot add record to ",t_name); return; } unsigned long long update_id=mysql_insert_id(ptr_db); // pthread_mutex_unlock(&db_t_lock); printf("add record (%llu,%d) ok.",update_id,item); } the program output errors like: [Thread debugging using libthread_db enabled] [New Thread 0xb7ae3b70 (LWP 7712)] Hello world! [New Thread 0xb72d6b70 (LWP 7713)] [New Thread 0xb6ad5b70 (LWP 7714)] [New Thread 0xb62d4b70 (LWP 7715)] [Thread 0xb7ae3b70 (LWP 7712) exited] producer... producer... consumer...consumer...add record (31441,0) ok.add record (31442,1) ok.producer... producer... consumer...consumer...add record (31443,2) ok.add record (31444,3) ok.producer... producer... consumer...consumer...add record (31445,4) ok.add record (31446,5) ok.producer... producer... consumer...consumer...add record (31447,6) ok.add record (31448,7) ok.producer... Error in my_thread_global_end(): 2 threads didn't exit [Thread 0xb72d6b70 (LWP 7713) exited] [Thread 0xb6ad5b70 (LWP 7714) exited] [Thread 0xb62d4b70 (LWP 7715) exited] Program exited normally. and when i add pthread_mutex_lock in function addRecord_d,the error still exists. So what exactly the problem is?

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• MySQL Split Time Ranges into Smaller Chunks

  - by Neren

  Hello all, I've recently been tasked with finishing a PHP/MySQL web app when the developer quit last week. I'm no MySQL expert, so I apologize if this is an intensely simple question. I've searched SO for the better part of two days trying to find a relatively easy solution to my problem, which is as follows. Problem in a Nutshell: I have a MySQL table full of start and end datetime (GMT -5) & UNIX Timestamp values covering durations of irregular length and need to break/split/divide them into more-regular time chunks (5 minutes). I'm not after a count of row entries per time chunk/bucket/period, if that makes any sense. Data Example: started, ended, started_UNIX, ended_UNIX 2010-10-25 15:12:33, 2010-10-25 15:47:09, 1288033953, 1288036029 What I'm hoping to get: 2010-10-25 15:12:33, 2010-10-25 15:15:00, 1288033953, 1288037700 2010-10-25 15:15:00, 2010-10-25 15:20:00, 1288037700, 1288038000 2010-10-25 15:20:00, 2010-10-25 15:25:00, 1288038000, 1288038300 2010-10-25 15:25:00, 2010-10-25 15:30:00, 1288038300, 1288038600 2010-10-25 15:30:00, 2010-10-25 15:35:00, 1288038600, 1288038900 2010-10-25 15:35:00, 2010-10-25 15:40:00, 1288038900, 1288039200 2010-10-25 15:40:00, 2010-10-25 15:45:00, 1288039200, 1288039500 2010-10-25 15:45:00, 2010-10-25 15:47:09, 1288039500, 1288039629 If you're interested, here's the quick & dirty on the app and why I need the data: App overview: The application receives very simple POST requests generated by a basic sensor device when its input pins go to ground, which submits an INSERT query to the database where MySQL records a timestamp (as started). When the input pins return from a grounded state, the device submits a different POST request, which causes the PHP app to submit an UPDATE query, where a modification time timestamp is inserted (as ended). My employer recently changed the periodic reporting unit of measure from Seconds "On" Per Day to Seconds "On" Per 5 Minute Interval. I had formulated what I thought would be a workable solution, but when I looked at it on paper, it looked like Rube Goldberg's nightmare constructed in MySQL, so that was out. Any suggestions as to how to break these spans into 5 minute blocks? Keeping it all in MySQL would be my preference, though I'll take any suggestions. Thank you for any suggestions you may have. Again, I apologize if this is a no-brainer. If I ask any additional questions of the SO collective consciousness in the future, I'll try to word them a bit better. Any help will be happily welcomed. Thanks, Neren

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• How do I access the enumerated item with an indexer and assign array string to it for display?

  - by g00p3k

  EDITED: Updated 3/23/09. See rest of post at bottom. I'm still having trouble with the indexer. Anymore help or examples would really help me out. Write a class, MyCourses, that contains an enumeration of all the courses that you are currently taking. This enum should be nested inside of your class MyCourses. Your class should also have an array field that provides a short description (as a String) of each of your courses. Write an indexer that takes one of your enumerated courses as an index and returns the String description of the course. Write a class MyFriends that contains an indexer that provides access to the names of your friends. namespace IT274_Unit4Project { public class MyCourses { // enumeration that contains an enumeration of all the courses that // student is currently enrolled in public enum CourseName {IT274= 0,CS210 = 1} // array field that provides short description for each of classes, // returns string description of the course private String[] courseDescription = {"Intermediate C#: Teaches intermediate elements of C# programming and software design", "Career Development Strategies: Teaches principles for career progression, resume preparation, and overall self anaylsis"}; // indexer that takes one of the enumerated courses as an index // and returns the String description of the course public String this[CourseName index] { get { if (index == 1) return courseDescription[0]; else return courseDescription[1]; } set { if (index == 1) courseDescription[0] = value; else courseDescription[1] = value; } } } }//end public class MyCourses I'm working on this homework project and having trouble understanding the text explaining how to correctly take the accessed value of the enumeration and then apply the string array value to it. Can you please help me understand this? The text we are using is very difficult and poorly written for a beginner to understand, so I'm kind of on my own here. I've got the first parts written, but need some help on the accessing of the enumeration value and assigning, i think i'm close, but don't understand how to properly get and set the values on this. Please do not provide me with direct code answers, unless a MSDN style explanation that is generalized and not specific to my project. ie: public class MyClass { string field1; string field2; //properties public string Value1 get etc... Thanks!

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• C++ include statement required if defining a map in a headerfile.

  - by Justin

  I was doing a project for computer course on programming concepts. This project was to be completed in C++ using Object Oriented designs we learned throughout the course. Anyhow, I have two files symboltable.h and symboltable.cpp. I want to use a map as the data structure so I define it in the private section of the header file. I #include <map> in the cpp file before I #include "symboltable.h". I get several errors from the compiler (MS VS 2008 Pro) when I go to debug/run the program the first of which is: Error 1 error C2146: syntax error : missing ';' before identifier 'table' c:\users\jsmith\documents\visual studio 2008\projects\project2\project2\symboltable.h 22 Project2 To fix this I had to #include <map> in the header file, which to me seems strange. Here are the relevant code files: // symboltable.h #include <map> class SymbolTable { public: SymbolTable() {} void insert(string variable, double value); double lookUp(string variable); void init(); // Added as part of the spec given in the conference area. private: map<string, double> table; // Our container for variables and their values. }; and // symboltable.cpp #include <map> #include <string> #include <iostream> using namespace std; #include "symboltable.h" void SymbolTable::insert(string variable, double value) { table[variable] = value; // Creates a new map entry, if variable name already exist it overwrites last value. } double SymbolTable::lookUp(string variable) { if(table.find(variable) == table.end()) // Search for the variable, find() returns a position, if thats the end then we didnt find it. throw exception("Error: Uninitialized variable"); else return table[variable]; } void SymbolTable::init() { table.clear(); // Clears the map, removes all elements. }

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• How to manually (bitwise) perform (float)x? (homework)

  - by Silver

  Now, here is the function header of the function I'm supposed to implement: /* * float_from_int - Return bit-level equivalent of expression (float) x * Result is returned as unsigned int, but * it is to be interpreted as the bit-level representation of a * single-precision floating point values. * Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while * Max ops: 30 * Rating: 4 */ unsigned float_from_int(int x) { ... } We aren't allowed to do float operations, or any kind of casting. Now I tried to implement the first algorithm given at this site: http://locklessinc.com/articles/i2f/ Here's my code: unsigned float_from_int(int x) { // grab sign bit int xIsNegative = 0; int absValOfX = x; if(x < 0){ xIsNegative = 1; absValOfX = -x; } // zero case if(x == 0){ return 0; } //int shiftsNeeded = 0; /*while(){ shiftsNeeded++; }*/ unsigned I2F_MAX_BITS = 15; unsigned I2F_MAX_INPUT = ((1 << I2F_MAX_BITS) - 1); unsigned I2F_SHIFT = (24 - I2F_MAX_BITS); unsigned result, i, exponent, fraction; if ((absValOfX & I2F_MAX_INPUT) == 0) result = 0; else { exponent = 126 + I2F_MAX_BITS; fraction = (absValOfX & I2F_MAX_INPUT) << I2F_SHIFT; i = 0; while(i < I2F_MAX_BITS) { if (fraction & 0x800000) break; else { fraction = fraction << 1; exponent = exponent - 1; } i++; } result = (xIsNegative << 31) | exponent << 23 | (fraction & 0x7fffff); } return result; } But it didn't work (see test error below): Test float_from_int(-2147483648[0x80000000]) failed... ...Gives 0[0x0]. Should be -822083584[0xcf000000] 4 4 0 float_times_four I don't know where to go from here. How should I go about parsing the float from this int?

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• ocjective-c Obtain return value from public method

  - by Felix

  I'm pretty new to objective-C (and C in general) and iPhone development and am coming from the java island, so there are some fundamentals that are quite tough to learn for me. I'm diving right into iOS5 and want to use storyboards. For now I am trying to setup a list in a UITableViewController that will be filled with values returned by a web service in the future. For now, I just want to generate some mock objects and show their names in the list to be able to proceed. Coming from java, my first approach would be to create a new Class that provides a global accessible method to generate some objects for my list: #import <Foundation/Foundation.h> @interface MockObjectGenerator : NSObject +(NSMutableArray *) createAndGetMockProjects; @end Implementation is... #import "MockObjectGenerator.h" // Custom object with some fields #import "Project.h" @implementation MockObjectGenerator + (NSMutableArray *) createAndGetMockObjects { NSMutableArray *mockProjects = [NSMutableArray alloc]; Project *project1 = [Project alloc]; Project *project2 = [Project alloc]; Project *project3 = [Project alloc]; project1.name = @"Project 1"; project2.name = @"Project 2"; project3.name = @"Project 3"; [mockProjects addObject:project1]; [mockProjects addObject:project2]; [mockProjects addObject:project3]; } And here is my ProjectTable.h that is supposed to control my ListView #import <UIKit/UIKit.h> @interface ProjectsTable : UITableViewController @property (strong, nonatomic) NSMutableArray *projectsList; @end And finally ProjectTable.m #import "ProjectsTable.h" #import "Project.h" #import "MockObjectGenerator.h" @interface ProjectsTable { @synthesize projectsList = _projectsList; -(id)initWithStyle:(UITableViewStyle:style { self = [super initWithStyle:style]; if (self) { _projectsList = [[MockObjectGenerator createAndGetMockObjects] copy]; } return self; } - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { // only one section for all return 1; - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { NSLog(@"%d entries in list", _projectsList.count); return _projectsList.count; - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { // the identifier of the lists prototype cell is set to this string value static NSString *CellIdentifier = @"projectCell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; Project *project = [_projectsList objectAtIndex:indexPath.row]; cell.textLabel.text = project.name } So while I think everything is correctly set, I expect the tableView to show my three mock objects in its rows. But it stays empty and the NSLog method prints "0 entries in list" into the console. So what am I doing wrong? Any help is appreciated. Best regards Felix

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• go programming POST FormValue can't be printed

  - by poor_programmer

  Before I being a bit of background, I am very new to go programming language. I am running go on Win 7, latest go package installer for windows. I'm not good at coding but I do like some challenge of learning a new language. I wanted to start learn Erlang but found go very interesting based on the GO I/O videos in youtube. I'm having problem with capturing POST form values in GO. I spend three hours yesterday to get go to print a POST form value in the browser and failed miserably. I don't know what I'm doing wrong, can anyone point me to the right direction? I can easily do this in another language like C#, PHP, VB, ASP, Rails etc. I have search the entire interweb and haven't found a working sample. Below is my sample code. Here is Index.html page {{ define "title" }}Homepage{{ end }} {{ define "content" }} <h1>My Homepage</h1> <p>Hello, and welcome to my homepage!</p> <form method="POST" action="/"> <p> Enter your name : <input type="text" name="username"> </P> <p> <button>Go</button> </form> <br /><br /> {{ end }} Here is the base page <!DOCTYPE html> <html lang="en"> <head> <title>{{ template "title" . }}</title> </head> <body> <section id="contents"> {{ template "content" . }} </section> <footer id="footer"> My homepage 2012 copy </footer> </body> </html> now some go code package main import ( "fmt" "http" "strings" "html/template" ) var index = template.Must(template.ParseFiles( "templates/_base.html", "templates/index.html", )) func GeneralHandler(w http.ResponseWriter, r *http.Request) { index.Execute(w, nil) if r.Method == "POST" { a := r.FormValue("username") fmt.Fprintf(w, "hi %s!",a); //<-- this variable does not rendered in the browser!!! } } func helloHandler(w http.ResponseWriter, r *http.Request) { remPartOfURL := r.URL.Path[len("/hello/"):] fmt.Fprintf(w, "Hello %s!", remPartOfURL) } func main() { http.HandleFunc("/", GeneralHandler) http.HandleFunc("/hello/", helloHandler) http.ListenAndServe("localhost:81", nil) } Thanks! PS: Very tedious to add four space before every line of code in stackoverflow especially when you are copy pasting. Didn't find it very user friendly or is there an easier way?

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• Copy constructor bug

  - by user168715

  I'm writing a simple nD-vector class, but am encountering a strange bug. I've stripped out the class to the bare minimum that still reproduces the bug: #include <iostream> using namespace std; template<unsigned int size> class nvector { public: nvector() {data_ = new double[size];} ~nvector() {delete[] data_;} template<unsigned int size2> nvector(const nvector<size2> &other) { data_ = new double[size]; int i=0; for(; i<size && i < size2; i++) data_[i] = other[i]; for(; i<size; i++) data_[i] = 0; } double &operator[](int i) {return data_[i];} const double&operator[](int i) const {return data_[i];} private: const nvector<size> &operator=(const nvector<size> &other); //Intentionally unimplemented for now double *data_; }; int main() { nvector<2> vector2d; vector2d[0] = 1; vector2d[1] = 2; nvector<3> vector3d(vector2d); for(int i=0; i<3; i++) cout << vector3d[i] << " "; cout << endl; //Prints 1 2 0 nvector<3> other3d(vector3d); for(int i=0; i<3; i++) cout << other3d[i] << " "; cout << endl; //Prints 1 2 0 } //Segfault??? On the surface this seems to work fine, and both tests print out the correct values. However, at the end of main the program crashes with a segfault, which I've traced to nvector's destructor. At first I thought the (incorrect) default assignment operator was somehow being called, which is why I added the (currently) unimplemented explicit assignment operator to rule this possibility out. So my copy constructor must be buggy, but I'm having one of those days where I'm staring at extremely simple code and just can't see it. Do you guys have any ideas?

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• CodeIgniter Form Validation

  - by mmcglynn

  I am trying to set up validation on a simple contact form that is created using the form helper. No validation at all occurs. What is wrong? In the code below, the “good” keyword always shows, regardless of what is entered into the form, and the saved values set via set_value are never shown. Controller // Contact function contact() { $data['pageTitle'] = "Contact"; $data['bodyId'] = "contact"; $this->load->library('form_validation'); $config_rules = array ('email' => 'required','message' => 'required'); $this->form_validation->set_rules($config_rules); if ($this->form_validation->run() == FALSE) { echo "bad"; $data['include'] = "v_contact"; $this->load->view('v_template',$data); } else { echo "good"; $data['include'] = "v_contact"; $this->load->view('v_template',$data); } } View echo validation_errors(); echo form_open('events/contact'); // name echo form_label('Name', 'name'); $data = array ( 'name' => 'name', 'id' => 'name', 'maxlength' => '64', 'size' => '40', 'value' => set_value('name') ); echo form_input($data) . "\n<br />"; // email address echo form_label('Email Address', 'email'); $data = array ( 'name' => 'email', 'id' => 'email', 'maxlength' => '64', 'size' => '40', 'value' => set_value('email') ); echo form_input($data) . "\n<br />"; // message echo form_label('Message', 'message'); $data = array ( 'name' => 'message', 'id' => 'message', 'rows' => '8', 'cols' => '35', 'value' => set_value('message') ); echo form_textarea($data) . "\n<br />"; echo form_submit('mysubmit', 'Send Message'); echo form_close();

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• Separation of domain and ui layer in a composite

  - by hansmaad

  Hi all, i'm wondering if there is a pattern how to separate the domain logic of a class from the ui responsibilities of the objects in the domain layer. Example: // Domain classes interface MachinePart { CalculateX(in, out) // Where do we put these: // Draw(Screen) ?? // ShowProperties(View) ?? // ... } class Assembly : MachinePart { CalculateX(in, out) subParts } class Pipe : MachinePart { CalculateX(in, out) length, diamater... } There is an application that calculates the value X for machines assembled from many machine parts. The assembly is loaded from a file representation and is designed as a composite. Each concrete part class stores some data to implement the CalculateX(in,out) method to simulate behaviour of the whole assembly. The application runs well but without GUI. To increase the usability a GUi should be developed on top of the existing implementation (changes to the existing code are allowed). The GUI should show a schematic graphical representation of the assembly and provide part specific dialogs to edit several parameters. To achieve these goals the application needs new functionality for each machine part to draw a schematic representation on the screen, show a property dialog and other things not related to the domain of machine simulation. I can think of some different solutions to implement a Draw(Screen) functionality for each part but i am not happy with each of them. First i could add a Draw(Screen) method to the MachinePart interface but this would mix-up domain code with ui code and i had to add a lot of functionality to each machine part class what makes my domain model hard to read and hard to understand. Another "simple" solution is to make all parts visitable and implement ui code in visitors but Visitor does not belong to my favorite patterns. I could derive UI variants from each machine part class to add the UI implementation there but i had to check if each part class is suited for inheritance and had to be careful on changes to the base classes. My currently favorite design is to create a parallel composite hierarchy where each component stores data to define a machine part, has implementation for UI methods and a factory method which creates instances of the corresponding domain classes, so that i can "convert" a UI assembly to a domain assembly. But there are problems to go back from the created domain hierarchy to the UI hierarchy for showing calculation results in the drawing for example (imagine some parts store some values during the calculation i want to show in the schematic representation after the simluation). Maybe there are some proven patterns for such problems?

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• SQL-How to retrieve the correct data using php

  - by Programatt

  I am new to SQL so please excuse my question if it is simple. I have a database with a few tables. 1 is a users table, the others are application tables that contain the users preferences for receiving notifications about that application based on the country they are interested in. What I want to do, is retrieve the e-mail address of all users that have an interest in that country. I am struggling to think about how to do this. I currently have the following query constructed, and the code to populate the values function check($string) { if (isset($_POST[$string])) { $print = implode(', ', $_POST[$string]); //Converts an array into a single string $imanageSQLArr = Array(); if (substr_count($print,'Benelux') > 0) { $imanageSQLArr[0] = "checked"; } else { $imanageSQLArr[0] = "off"; } if (substr_count($print, 'France') > 0) { $imanageSQLArr[1] = "checked"; } else { $imanageSQLArr[1] = "off"; } if (substr_count($print, 'Germany') > 0) { $imanageSQLArr[2] = "checked"; } else { $imanageSQLArr[2] = "off"; } if (substr_count($print, 'Italy') > 0) { $imanageSQLArr[3] = "checked"; } else { $imanageSQLArr[3] = "off"; } if (substr_count($print, 'Netherlands') > 0) { $imanageSQLArr[4] = "checked"; } else { $imanageSQLArr[4] = "off"; } if (substr_count($print, 'Portugal') > 0) { $imanageSQLArr[5] = "checked"; } else { $imanageSQLArr[5] = "off"; } if (substr_count($print, 'Spain') > 0) { $imanageSQLArr[6] = "checked"; } else { $imanageSQLArr[6] = "off"; } if (substr_count($print, 'Sweden') > 0) { $imanageSQLArr[7] = "checked"; } else { $imanageSQLArr[7] = "off"; } if (substr_count($print, 'Switzerland') > 0) { $imanageSQLArr[8] = "checked"; } else { $imanageSQLArr[8] = "off"; } if (substr_count($print, 'UK') > 0) { $imanageSQLArr[9] = "checked"; } else { $imanageSQLArr[9] = "off"; } and the query $tocheck = $db->prepare( "SELECT users.email FROM users,app WHERE users.id=app.userid AND BENELUX=:BENELUX AND FRANCE=:FRANCE AND GERMANY=:GERMANY AND ITALY=:ITALY AND NETHERLANDS=:NETHERLANDS AND PORTUGAL=:PORTUGAL AND SPAIN=:SPAIN AND SWEDEN=:SWEDEN AND SWITZERLAND=:SWITZERLAND AND UK=:UK"); $tocheck->execute($country); $row = $tocheck->fetchAll(); This does retrieve data, but only people who's preferences match EXACTLY what is put (so what they haven't selected is taken into account as much as what they have). Any help would be greatly appreciated.

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• how can we change the value by using radio buttons

  - by magna

  I am making a website in Adobe Dreamweaver with php. In the site there’s a 3 buttons for selecting payment method that will act as the continue button. What I want is when the user checks a radio buttons (I agree button), it will be add with that amount and display with previous amount.. there is three buttons which has the corresponding values(amount in pounds).. plz check my website http://www.spsmobile.co.uk in this linkgo to mobile phone unlocking and after add the cart click make payment it will go to next page there is a delivery mail details.. for that delivery mail details only am asking.. here i mentioned code: <input id="radio-1" type="radio" name="rmr" value="1"> <label for="radio-1">£3</label> <input id="radio-2" type="radio" name="rmr" value="2"> <label for="radio-2">£5.5</label> <input id="radio-3" type="radio" name="rmr" value="4"> <label for="radio-3">£10</label> <div class="total-text" style="font-size:36px">£10</div> var total = parseInt($("div.total-text").text().substring(1), 10); $("input[name='rmr']").bind('change', function() { var amount = 0; switch (this.value) { case "1": amount = 3; break; case "2": amount = 5.5; break; case "4": amount = 10; break; } $("div.total-text").text("£" + (total + amount)); }); but there is no change , my previous amount did not add with that. while am clicking previous amount only displayed on browser.. i need when i cliks radio button the value should change correspondingly.. where i did that mistake...plz give me some idea and what should i do..is there any need for storing db.. thanks in adv

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• Two collections and a for loop. (Urgent help needed) Checking an object variable against an inputted

  - by Elliott

  Hi there, I'm relatively new to java, I'm certain the error is trivial. But can't for the life of me spot it. I have an end of term exam on monday and currently trying to get to grips with past papers! Anyway heregoes, in another method (ALGO_1) I search over elements of and check the value H_NAME equals a value entered in the main. When I attempt to run the code I get a null pointer exception, also upon trying to print (with System.out.println etc) the H_NAME value after each for loop in the snippet I also get a null statement returned to me. I am fairly certain that the collection is simply not storing the data gathered up by the Scanner. But then again when I check the collection size with size() it is about the right size. Either way I'm pretty lost and would appreciate the help. Main questions I guess to ask are: from the readBackground method is the data.add in the wrong place? is the snippet simply structured wrongly? oh and another point when I use System.out.println to check the Background object values name, starttime, increment etc they print out fine. Thanks in advance.(PS im guessing the formatting is terrible, apologies.) snippet of code: for(Hydro hd: hydros){ System.out.println(hd.H_NAME); for(Background back : backgs){ System.out.println(back.H_NAME); if(back.H_NAME.equals(hydroName)){ //get error here public static Collection<Background> readBackground(String url) throws IOException { URL u = new URL(url); InputStream is = u.openStream(); InputStreamReader isr = new InputStreamReader(is); BufferedReader b = new BufferedReader(isr); String line =""; Vector<Background> data = new Vector<Background>(); while((line = b.readLine())!= null){ Scanner s = new Scanner(line); String name = s.next(); double starttime = Double.parseDouble(s.next()); double increment = Double.parseDouble(s.next()); double sum = 0; double p = 0; double nterms = 0; while((s.hasNextDouble())){ p = Double.parseDouble(s.next()); nterms++; sum += p; } double pbmean = sum/nterms; Background SAMP = new Background(name, starttime, increment, pbmean); data.add(SAMP); } return data; } Edit/Delete Message

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• representing an XML config file with an IXmlSerializable class

  - by Sarah Vessels

  I'm writing in C# and trying to represent an XML config file through an IXmlSerializable class. I'm unsure how to represent the nested elements in my config file, though, such as logLevel: <?xml version="1.0" encoding="utf-8" ?> <configuration> <logging> <logLevel>Error</logLevel> </logging> <credentials> <user>user123</user> <host>localhost</host> <password>pass123</password> </credentials> <credentials> <user>user456</user> <host>my.other.domain.com</host> <password>pass456</password> </credentials> </configuration> There is an enum called LogLevel that represents all the possible values for the logLevel tag. The tags within credentials should all come out as strings. In my class, called DLLConfigFile, I had the following: [XmlElement(ElementName="logLevel", DataType="LogLevel")] public LogLevel LogLevel; However, this isn't going to work because <logLevel> isn't within the root node of the XML file, it's one node deeper in <logging>. How do I go about doing this? As for the <credentials> nodes, my guess is I will need a second class, say CredentialsSection, and have a property such as the following: [XmlElement(ElementName="credentials", DataType="CredentialsSection")] public CredentialsSection[] AllCredentials; Edit: okay, I tried Robert Love's suggestion and created a LoggingSection class. However, my test fails: var xs = new XmlSerializer(typeof(DLLConfigFile)); using (var stream = new FileStream(_configPath, FileMode.Open, FileAccess.Read, FileShare.Read)) { using (var streamReader = new StreamReader(stream)) { XmlReader reader = new XmlTextReader(streamReader); var file = (DLLConfigFile)xs.Deserialize(reader); Assert.IsNotNull(file); LoggingSection logging = file.Logging; Assert.IsNotNull(logging); // fails here LogLevel logLevel = logging.LogLevel; Assert.IsNotNull(logLevel); Assert.AreEqual(EXPECTED_LOG_LEVEL, logLevel); } } The config file I'm testing with definitely has <logging>. Here's what the classes look like: [Serializable] [XmlRoot("logging")] public class LoggingSection : IXmlSerializable { public XmlSchema GetSchema() { return null; } [XmlElement(ElementName="logLevel", DataType="LogLevel")] public LogLevel LogLevel; public void ReadXml(XmlReader reader) { LogLevel = (LogLevel)Enum.Parse(typeof(LogLevel), reader.ReadString()); } public void WriteXml(XmlWriter writer) { writer.WriteString(Enum.GetName(typeof(LogLevel), LogLevel)); } } [Serializable] [XmlRoot("configuration")] public class DLLConfigFile : IXmlSerializable { [XmlElement(ElementName="logging", DataType="LoggingSection")] public LoggingSection Logging; }

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• When mocking a class with Moq, how can I CallBase for just specific methods?

  - by Daryn

  I really appreciate Moq's Loose mocking behaviour that returns default values when no expectations are set. It's convenient and saves me code, and it also acts as a safety measure: dependencies won't get unintentionally called during the unit test (as long as they are virtual). However, I'm confused about how to keep these benefits when the method under test happens to be virtual. In this case I do want to call the real code for that one method, while still having the rest of the class loosely mocked. All I have found in my searching is that I could set mock.CallBase = true to ensure that the method gets called. However, that affects the whole class. I don't want to do that because it puts me in a dilemma about all the other properties and methods in the class that hide call dependencies: if CallBase is true then I have to either Setup stubs for all of the properties and methods that hide dependencies -- Even though my test doesn't think it needs to care about those dependencies, or Hope that I don't forget to Setup any stubs (and that no new dependencies get added to the code in the future) -- Risk unit tests hitting a real dependency. Q: With Moq, is there any way to test a virtual method, when I mocked the class to stub just a few dependencies? I.e. Without resorting to CallBase=true and having to stub all of the dependencies? Example code to illustrate (uses MSTest, InternalsVisibleTo DynamicProxyGenAssembly2) In the following example, TestNonVirtualMethod passes, but TestVirtualMethod fails - returns null. public class Foo { public string NonVirtualMethod() { return GetDependencyA(); } public virtual string VirtualMethod() { return GetDependencyA();} internal virtual string GetDependencyA() { return "! Hit REAL Dependency A !"; } // [... Possibly many other dependencies ...] internal virtual string GetDependencyN() { return "! Hit REAL Dependency N !"; } } [TestClass] public class UnitTest1 { [TestMethod] public void TestNonVirtualMethod() { var mockFoo = new Mock<Foo>(); mockFoo.Setup(m => m.GetDependencyA()).Returns(expectedResultString); string result = mockFoo.Object.NonVirtualMethod(); Assert.AreEqual(expectedResultString, result); } [TestMethod] public void TestVirtualMethod() // Fails { var mockFoo = new Mock<Foo>(); mockFoo.Setup(m => m.GetDependencyA()).Returns(expectedResultString); // (I don't want to setup GetDependencyB ... GetDependencyN here) string result = mockFoo.Object.VirtualMethod(); Assert.AreEqual(expectedResultString, result); } string expectedResultString = "Hit mock dependency A - OK"; }

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• C++ Template const char array to int

  - by Levi Schuck

  So, I'm wishing to be able to have a static const compile time struct that holds some value based on a string by using templates. I only desire up to four characters. I know that the type of 'abcd' is int, and so is 'ab','abc', and although 'a' is of type char, it works out for a template<int v> struct What I wish to do is take sizes of 2,3,4,5 of some const char, "abcd" and have the same functionality as if they used 'abcd'. Note that I do not mean 1,2,3, or 4 because I expect the null terminator. cout << typeid("abcd").name() << endl; tells me that the type for this hard coded string is char const [5], which includes the null terminator on the end. I understand that I will need to twiddle the values as characters, so they are represented as an integer. I cannot use constexpr since VS10 does not support it (VS11 doesn't either..) So, for example with somewhere this template defined, and later the last line template <int v> struct something { static const int value = v; }; //Eventually in some method cout << typeid(something<'abcd'>::value).name() << endl; works just fine. I've tried template<char v[5]> struct something2 { static const int value = v[0]; } template<char const v[5]> struct something2 { static const int value = v[0]; } template<const char v[5]> struct something2 { static const int value = v[0]; } All of them build individually, though when I throw in my test, cout << typeid(something2<"abcd">::value).name() << endl; I get 'something2' : invalid expression as a template argument for 'v' 'something2' : use of class template requires template argument list Is this not feasible or am I misunderstanding something?

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• C# Type Casting at Runtimefor Array.SetValue

  - by sprocketonline

  I'm trying to create an array using reflection, and insert values into it. I'm trying to do this for many different types so would like a createAndFillArray function capable of this : Type t1 = typeof(A); Type t2 = typeof(B); double exampleA = 22.5; int exampleB = 43; Array arrA = createAndFillArray(t1, exampleA); Array arrB = createAndFillArray(t2, exampleB); private Array createAndFillArray(Type t, object val){ Array arr = Array.CreateInstance( t, 1); //length 1 in this example only, real-world is of variable length. arr.SetValue( val, 0 ); //this causes the following error: "System.InvalidCastException : Object cannot be stored in an array of this type." return arr; } with the class A being as follows: public class A{ public A(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator A(double d){ A a = new A(); a.Value = d; return a; } } and class B being very similar, but with int: public class B{ public B(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator B(double d){ B b = new B(); b.Value = d; return b; } } I hoped that the implicit operator would have ensured that the double be converted to class A, or the int to class B, and the error avoided; but this is obviously not so. The above is used in a custom deserialization class, which takes data from a custom data format and fills in the corresponding .Net object properties. I'm doing this via reflection and at runtime, so I think both are unavoidable. I'm targeting the C# 2.0 framework. I've dozens, if not hundreds, of classes similar to A and B, so would prefer to find a solution which improved on the createAndFillArray method rather than a solution which altered these classes.

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• Techniques for querying a set of object in-memory in a Java application

  - by Edd Grant

  Hi All, We have a system which performs a 'coarse search' by invoking an interface on another system which returns a set of Java objects. Once we have received the search results I need to be able to further filter the resulting Java objects based on certain criteria describing the state of the attributes (e.g. from the initial objects return all objects where x.y z && a.b == c). The criteria used to filter the set of objects each time is partially user configurable, by this I mean that users will be able to select the values and ranges to match on but the attributes they can pick from will be a fixed set. The data sets are likely to contain <= 10,000 objects for each search. The search will be executed manually by the application user base probably no more than 2000 times a day (approx). It's probably worth mentioning that all the objects in the result set are known domain object classes which have Hibernate and JPA annotations describing their structure and relationship. Off the top of my head I can think of 3 ways of doing this: For each search persist the initial result set objects in our database, then use Hibernate to re-query them using the finer grained criteria. Use an in-memory Database (such as hsqldb?) to query and refine the initial result set. Write some custom code which iterates the initial result set and pulls out the desired records. Option 1 seems to involve a lot of toing and froing across a network to a physical Database (Oracle 10g) which might result in a lot of network and disk activity. It would also require the results from each search to be isolated from other result sets to ensure that different searches don't interfere with each other. Option 2 seems like a good idea in principle as it would allow me to do the finer query in memory and would not require the persistence of result data which would only be discarded after the search was complete. Gut feeling is that this could be pretty performant too but might result in larger memory overheads (which is fine as we can be pretty flexible on the amount of memory our JVM gets). Option 3 could be very performant but is something I would like to avoid as any code we write would require such careful testing that the time taken to acheive something flexible and robust enough would probably be prohibitive. I don't have time to prototype all 3 ideas so I am looking for comments people may have on the 3 options above, plus any further ideas I have not considered, to help me decide which idea might be most suitable. I'm currently leaning toward option 2 (in memory database) so would be keen to hear from people with experience of querying POJOs in memory too. Hopefully I have described the situation in enough detail but don't hesitate to ask if any further information is required to better understand the scenario. Cheers, Edd

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• Incorrect string encodings

  - by James

  Note: I have read all of the related PHP, UTF-8, character encoding articles that are usually suggested, but my question relates to data inserted before I applied such techniques. I am wishing to retrospectively fix all character encoding problems. Now all connections are set as utf8 using PDO. PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8' Unfortunately, a large amount of data was inserted that is of questionable encoding before I had implemented correct character encoding practices. As displayed by: $sql = "SELECT name FROM data LIMIT 3"; foreach ($pdo->query($sql) as $row) { $name = $row['name']; echo $name . "\n"; echo utf8_encode($name) . "\n"; echo utf8_decode($name) . "\n"; echo htmlspecialchars($name, ENT_QUOTES, 'UTF-8') . "\n"; echo htmlspecialchars(utf8_encode($name), ENT_QUOTES, 'UTF-8') . "\n"; echo htmlspecialchars(utf8_decode($name), ENT_QUOTES, 'UTF-8') . "\n"; echo '<hr/>'; } Which produces: Antonín Dvořák AntonÃÆín DvoÃâ¦Ãâ¢ÃÆák Anton??­n Dvo??????¡k Antonín Dvořák AntonÃÆín DvoÃâ¦Ãâ¢ÃÆák ---------- Ô±Ö€Õ¡Õ´ Ô½Õ¡Õ¹Õ¡Õ¿Ö€ÕµÕ¡Õ¶ ñÃâ¬Ã¡Ã´ ýáùáÿÃâ¬ÃµÃ¡Ã¶ ????? ?????????? Ô±Ö€Õ¡Õ´ Ô½Õ¡Õ¹Õ¡Õ¿Ö€ÕµÕ¡Õ¶ ñÃâ¬Ã¡Ã´ ýáùáÿÃâ¬ÃµÃ¡Ã¶ ---------- Tiësto Tiësto Tiësto Tiësto Tiësto Tiësto ---------- When removing 'SET NAMES utf8' with PDO it produces the data: Antonín DvoÅák Antonín DvoÃÂák Antonín Dvorák Antonín DvoÅák Antonín DvoÃÂák Antonín Dvorák ---------- ???? ????????? Ô±ÖÕ¡Õ´ Ô½Õ¡Õ¹Õ¡Õ¿ÖÕµÕ¡Õ¶ ???? ????????? ???? ????????? Ô±ÖÕ¡Õ´ Ô½Õ¡Õ¹Õ¡Õ¿ÖÕµÕ¡Õ¶ ???? ????????? ---------- Tiësto Tiësto Ti?sto Tiësto Tiësto ---------- And here is a dump of the database rows concerned: DROP TABLE IF EXISTS `data`; CREATE TABLE IF NOT EXISTS `data` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(80) NOT NULL, PRIMARY KEY (`id`), KEY `name` (`name`(10)), ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=0; INSERT INTO `data` (`id`, `name`) VALUES (0, 'Antonín Dvořák'), (1, 'Ô±Ö€Õ¡Õ´ Ô½Õ¡Õ¹Õ¡Õ¿Ö€ÕµÕ¡Õ¶'), (2, 'Tiësto'); The 3rd and 6th lines of the 3rd row "Tiësto" are then correctly echoed. I'm just unsure what is the best way to correct encodings/detect the encodings of bad strings and correct, etc.

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• Avoiding explicit recursion in Haskell

  - by Travis Brown

  The following simple function applies a given monadic function iteratively until it hits a Nothing, at which point it returns the last non-Nothing value. It does what I need, and I understand how it works. lastJustM :: (Monad m) => (a -> m (Maybe a)) -> a -> m a lastJustM g x = g x >>= maybe (return x) (lastJustM g) As part of my self-education in Haskell I'm trying to avoid explicit recursion (or at least understand how to) whenever I can. It seems like there should be a simple non-explicitly recursive solution in this case, but I'm having trouble figuring it out. I don't want something like a monadic version of takeWhile, since it could be expensive to collect all the pre-Nothing values, and I don't care about them anyway. I checked Hoogle for the signature and nothing shows up. The m (Maybe a) bit makes me think a monad transformer might be useful here, but I don't really have the intuitions I'd need to come up with the details (yet). It's probably either embarrassingly easy to do this or embarrassingly easy to see why it can't or shouldn't be done, but this wouldn't be the first time I've used self-embarrassment as a pedagogical strategy. Background: Here's a simplified working example for context: suppose we're interested in random walks in the unit square, but we only care about points of exit. We have the following step function: randomStep :: (Floating a, Ord a, Random a) => a -> (a, a) -> State StdGen (Maybe (a, a)) randomStep s (x, y) = do (a, gen') <- randomR (0, 2 * pi) <$> get put gen' let (x', y') = (x + s * cos a, y + s * sin a) if x' < 0 || x' > 1 || y' < 0 || y' > 1 then return Nothing else return $ Just (x', y') Something like evalState (lastJustM (randomStep 0.01) (0.5, 0.5)) <$> newStdGen will give us a new data point.

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• Selenium navigation inside foreach loop

  - by smudgedlens

  I am having an issue with navigation. I get a list of rows from an html table. I iterate over the rows and scrape information from them. But there is also a link on the row that I click to go to more information related to the row to scrape. Then I navigate back to the page with the original table. This works for the first row, but for the subsequent rows, it throws an exception. I look at my row collection after the first time the link inside a row is clicked, and none of them have the correct values like they did before I clicked the link. I believe that there is something going on when I navigate to a different URL that I'm not getting. My code is below. How do I get this working so I can iterate over the parent table, click the links in each row, navigate to the child table, but still continue iterating over the rows in the parent table? private List<Document> getResults() { var documents = new List<Document>(); //Results IWebElement docsTable = this.webDriver.FindElements(By.TagName("table")) .Where(table => table.Text.Contains("Document List")) .FirstOrDefault(); var validDocRowRegex = new Regex(@"^(\d{3}\s+)"); var docRows = docsTable.FindElements(By.TagName("tr")) .Where(row => //It throws an exception with .FindElement() when there isn't one. row.FindElements(By.TagName("td")).FirstOrDefault() != null && //Yeah, I don't get this one either. I negate the match and so it works?? !validDocRowRegex.IsMatch( row.FindElement(By.TagName("td")).Text)) .ToList(); foreach (var docRow in docRows) { //Todo: find out why this is crashing on some documents. var cells = docRow.FindElements(By.TagName("td")); var document = new Document { DocID = Convert.ToInt32(cells.First().Text), PNum = Convert.ToInt32(cells[1].Text), AuthNum = Convert.ToInt32(cells[2].Text) }; //Go to history for the current document. cells.Where(cell => cell.FindElements(By.TagName("a")).FirstOrDefault() != null) .FirstOrDefault().Click(); //Todo: scrape child table. this.webDriver.Navigate().Back(); } return documents; }

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