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• Is there a writable iterator in Java?

  - by Lukasz Lew

  In C+ one can use iterators for writing to a sequence. Simplest example would be: vector<int> v; for (vector<int>::iterator it = v.begin(); it!=v.end(); ++it) { *it = 42; } I need something more complicated - keep iterator as a class member for a later use. But I don't know how to get this behavior from Java iterators. Are there writable iterators in Java at all? If not then what replaces them?

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• C++ string sort like a human being?

  - by Walter Nissen

  I would like to sort alphanumeric strings the way a human being would sort them. I.e., "A2" comes before "A10", and "a" certainly comes before "Z"! Is there any way to do with without writing a mini-parser? Ideally it would also put "A1B1" before "A1B10". I see the question "Natural (human alpha-numeric) sort in Microsoft SQL 2005" with a possible answer, but it uses various library functions, as does "Sorting Strings for Humans with IComparer". Below is a test case that currently fails: #include <set> #include <iterator> #include <iostream> #include <vector> #include <cassert> template <typename T> struct LexicographicSort { inline bool operator() (const T& lhs, const T& rhs) const{ std::ostringstream s1,s2; s1 << toLower(lhs); s2 << toLower(rhs); bool less = s1.str() < s2.str(); std::cout<<s1.str()<<" "<<s2.str()<<" "<<less<<"\n"; return less; } inline std::string toLower(const std::string& str) const { std::string newString(""); for (std::string::const_iterator charIt = str.begin(); charIt!=str.end();++charIt) { newString.push_back(std::tolower(*charIt)); } return newString; } }; int main(void) { const std::string reference[5] = {"ab","B","c1","c2","c10"}; std::vector<std::string> referenceStrings(&(reference[0]), &(reference[5])); //Insert in reverse order so we know they get sorted std::set<std::string,LexicographicSort<std::string> > strings(referenceStrings.rbegin(), referenceStrings.rend()); std::cout<<"Items:\n"; std::copy(strings.begin(), strings.end(), std::ostream_iterator<std::string>(std::cout, "\n")); std::vector<std::string> sortedStrings(strings.begin(), strings.end()); assert(sortedStrings == referenceStrings); }

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• Icons in Silverlight: Images vs. Vectors

  - by Shnitzel

  I like using the vector drawing feature of Expression Blend to create icons. That way I can change colors easily on my icons without having to resort to an image editor. But my question is... Say I have a treeview control that has an icon next to each tree element and say I have hundreds of elements. Do you think using images is faster - performance wise than using vector icons? B/c I'd rather use vectors but I'm wondering about performance concerns.

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• C++ Static Initializer - Is it thread safe

  - by Yan Cheng CHEOK

  Usually, when I try to initialize a static variable class Test2 { public: static vector<string> stringList; private: static bool __init; static bool init() { stringList.push_back("string1"); stringList.push_back("string2"); stringList.push_back("string3"); return true; } }; // Implement vector<string> Test2::stringList; bool Test2::__init = Test2::init(); Is the following code thread safe, during static variable initialization? Is there any better way to static initialize stringlist, instead of using a seperate static function (init)?

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• Java and Different Types of Stacks

  - by Rarge

  Currently the only stack I know anything about is Vector, I normally use this in place of an array but I understand that there is other types of stacks and they all suit different jobs. The project I am currently working on requires me to be inserting objects in a certain position inside a stack, not always the front of the stack and I am under the impression that a Vector may not be the best class for this job. Could somebody please give me a brief description of the other types of stacks available to me with the Java language and their advantages and disadvantages? Are these names homogeneous? E.g. Are they only used in the Java language or are they used as general terms in Computer Science? Thank you

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• 3D Camera looking at arbitrary point, but never rolling to do so

  - by Nektarios

  (In C#/XNA 4.0) I have Vector3 cameraPosition, Vector3 targetPosition I want to have my camera look at the target, always 'facing' it, but never rolling So roll always is neutral, to view the target the camera always either adjusts pitch or yaw I've tried countless combinations of methods and information I find here and on the web but I haven't found anything that works properly. I think my issue may be my 'Up' vector (which I've tried .Up, 1,0,0, 0,1,0, 0,0,1) When I move my camera I do: CameraPosition += moveSpeed * vectorToAdd; UpdateViewMatrix(); UpdateViewMatrix() is.. well, I've tried everything I have seen. At most simple... View = Matrix.CreateLookAt(CameraPosition, targetPosition, upVector); Where upVector has been Vector3.Up, 1, 0, 0; 0, 1, 0; 0, 0, 1, or other more 'proper' attempts to get my actual up vector. This sounds like it's probably my problem.. This should be dead simple, help!

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• Botan::SecureVector - Destructor called in Constructor???

  - by sheepsimulator

  When using the Botan::SecureVector in the following unit test: void UnitTest() { std::vector<byte> vbData; vbData.push_back(0x04); vbData.push_back(0x04); vbData.push_back(0x04); Botan::SecureVector<Botan::byte> svData(&vbData[0], vbData.size()); CPPUNIT_ASSERT(vbData == std::vector<byte>(svData.begin(), svData.end())); } a segmentation fault occurs when trying to allocate the SecureVector.

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• Better way of enforcing this template?

  - by Dennis Ritchie

  Currently, I have a function template like this that converts a vector into a string (just a natural string, separating the elements with a comma): //the type T must be passable into std::to_string template<typename T> std::string vec_to_str(const std::vector<T> &vec); As you can see, this is only meant for vectors whose elements can be passed into the built-in std::to_string function (such as int, double, etc.) Is it considered a good practice to document with comments the allowed T? If not, what should I do? Is it possible to enforce this in a better way?

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• Generating a random displacement on the unit sphere

  - by becko

  Given a unit vector n, I need to generate, as fast as possible, another random unit vector m. The deviation of m from n should be on the order of a positive parameter sigma, and the distribution of m on the unit sphere should be symmetrical around n. I have no specific requirements on the representation of unit vectors, so you can use spherical angles, Cartesian coordinates, or whatever turns out to be convenient. Also, there are no precise requirements on the probability distributions used, as long as it decays when m deviates more than sigma from n. I am working with gsl and C. I have come up with a somewhat convoluted method using Cartesian coordinates. I will post it later if it is useful, but I would like to see people's ideas.

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• Unmangling the result of std::type_info::name

  - by terminus

  I'm currently working on some logging code that supposed to - among other things - print information about the calling function. This should be relatively easy, standard C++ has a type_info class. This contains the name of the typeid'd class/function/etc. but it's mangled. It's not very usefull. I.e. typeid(std::vector).name() returns "St6vectorIiSaIiEE". Is there a way to produce something usefull from this? Like 'std::vector' for the above example. If it only works for non-template classes, that's fine too. The sollution should work for gcc, but it would be better if I could port it. It's for logging so it's not so important that it can't be turned of, but it should be helpfull for debugging.

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• Multiple key map in c++

  - by Morgan

  Hi, I'm wondering if any of you know of a c++ associative map container type which I can perform multiple key lookups on. The map needs to have constant time lookups but I don't care if it's ordered or unordered. It just needs to be fast. For example, I want to store a bunch of std::vector objects in a map with an integer and a void* as the lookup keys. Both the int and the void* must match for my vector to be retrieved. Does anything like this exist already? Or am I going to have to roll my own. If so, any suggestions? I've been trying to store a boost::unordered_map inside another boost::unordered_map, but I have not had any success with this method yet. Maybe I will continue Pershing this method if there is no simpler way. Thanks!

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• check sequence in matlab

  - by gabboshow

  I have a vector that should contain n sequences from 00 to 11 A = [00;01;02;03;04;05;06;07;08;09;10;11;00;01;02;03;04;05;06;07;08;09;10;11] and I would like to check that the sequence "00 - 11 " is always respected (no missing values). for example if A =[00;01;02; 04;05;06;07;08;09;10;11;00;01;02;03;04;05;06;07;08;09;10;11] (missing 03 in the 3rd position) For each missing value I would like to have back this information in another vector missing= [value_1,position_1; value_2, position_2; etc, etc] Can you help me?

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• Best way to reduce consecutive NAs to single NA

  - by digEmAll

  I need to reduce the consecutive NA's in a vector to a single NA, without touching the other values. So, for example, given a vector like this: NA NA 8 7 NA NA NA NA NA 3 3 NA -1 4 what I need to get, is the following result: NA 8 7 NA 3 3 NA -1 4 Currently, I'm using the following function: reduceConsecutiveNA2One <- function(vect){ enc <- rle(is.na(vect)) # helper func tmpFun <- function(i){ if(enc$values[i]){ data.frame(L=c(enc$lengths[i]-1, 1), V=c(TRUE,FALSE)) }else{ data.frame(L=enc$lengths[i], V=enc$values[i]) } } Df <- do.call(rbind.data.frame,lapply(1:length(enc$lengths),FUN=tmpFun)) return(vect[rep.int(!Df$V,Df$L)]) } and it seems to work fine, but probably there's a simpler/faster way to accomplish this task. Any suggestions ? Thanks in advance.

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• Virtual methods as Comp function to sort

  - by wilsongoncalo.mp

  Hello everyone! I'm new to C++ and i'm trying to use std::sort function to sort a vector of Solutions. The code is something like this (solution list is a *vector): void SolutionSet::sort(Comparator &comparator) { std::sort(solutionsList_->begin(), solutionsList_->end(), &comparator::compare); } The comparator param is a Comparator´s child class instance , and the compare method is virtual at Comparator class and implemented by all Comparator's child classes. And i want to use that function as a comparator function at std:sort(). Is this possible? If it is, can someone tell me how? Because with the previous code, it doesn't work. If i've not made myself clear, please just ask! Thank you guys!

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• Contents changed(cleared?) when access the pointer returned by std::string::c_str()

  - by justamask

  string conf()     {         vector v;         //..         v = func(); //this function returns a vector         return v[1];     }     void test()     {         const char* p = conf().c_str();         // the string object will be alive as a auto var         // so the pointer should be valid till the end of this function,right?           // ... lots of steps, but none of them would access the pointer p         // when access p here, SOMETIMES the contents would change ... Why?         // the platform is solaris 64 bit         // compiler is sun workshop 12         // my code is compiled as  ELF 32-bit MSB relocatable SPARC32PLUS Version 1, V8+ Required         // but need to link with some shared lib which are ELF 32-bit MSB dynamic lib SPARC Version 1, dynamically linked, stripped     }

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• c++ std::ostringstream vs std::string::append

  - by NickSoft

  In all examples that use some kind of buffering I see they use stream instead of string. How is std::ostringstream and << operator different than using string.append. Which one is faster and which one uses less resourses (memory). One difference I know is that you can output different types into output stream (like integer) rather than the limited types that string::append accepts. Here is an example: std::ostringstream os; os << "Content-Type: " << contentType << ";charset=" << charset << "\r\n"; std::string header = os.str(); vs std::string header("Content-Type: "); header.append(contentType); header.append(";charset="); header.append(charset); header.append("\r\n"); Obviously using stream is shorter, but I think append returns reference to the string so it can be written like this: std::string header("Content-Type: "); header.append(contentType) .append(";charset=") .append(charset) .append("\r\n"); And with output stream you can do: std::string content; ... os << "Content-Length: " << content.length() << "\r\n"; But what about memory usage and speed? Especially when used in a big loop. Update: To be more clear the question is: Which one should I use and why? Is there situations when one is preferred or the other? For performance and memory ... well I think benchmark is the only way since every implementation could be different. Update 2: Well I don't get clear idea what should I use from the answers which means that any of them will do the job, plus vector. Cubbi did nice benchmark with the addition of Dietmar Kühl that the biggest difference is construction of those objects. If you are looking for an answer you should check that too. I'll wait a bit more for other answers (look previous update) and if I don't get one I think I'll accept Tolga's answer because his suggestion to use vector is already done before which means vector should be less resource hungry.

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• How to make this jpeg compression faster

  - by Richard Knop

  I am using OpenCV to compress binary images from a camera: vector<int> p; p.push_back(CV_IMWRITE_JPEG_QUALITY); p.push_back(75); // JPG quality vector<unsigned char> jpegBuf; cv::imencode(".jpg", fIplImageHeader, jpegBuf, p); The code above compresses a binary RGB image stored in fIplImageHeader to a JPEG image. For a 640*480 image it takes about 0.25 seconds to execute the five lines above. Is there any way I could make it faster? I really need to repeat the compression more than 4 times a second.

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• String vectors not working as expected with newline and iterators? (C++)

  - by kevin

  I have a text file made of 3 lines: Line 1 Line 3 (Line 1, a blank line, and Line 3) vector<string> text; vector<string>::iterator it; ifstream file("test.txt"); string str; while (getline(file, str)) { if (str.length() == 0) str = "\n"; // since getline discards the newline character, replacing blank strings with newline text.push_back(str); } // while for (it=text.begin(); it < text.end(); it++) cout << (*it); Prints out: Line 1 Line 3 I'm not sure why the string with only a newline was not printed out. Any help would be appreciated. Thanks.

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• How to change size of STL container in C++

  - by Jaime Pardos

  I have a piece of performance critical code written with pointers and dynamic memory. I would like to rewrite it with STL containers, but I'm a bit concerned with performance. Is there a way to increase the size of a container without initializing the data? For example, instead of doing ptr = new BYTE[x]; I want to do something like vec.insert(vec.begin(), x, 0); However this initializes every byte to 0. Isn't there a way to just make the vector grow? I know about reserve() but it just allocates memory, it doesn't change the size of the vector, and doesn't allows me to access it until I have inserted valid data. Thank you everyone.

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• troubles with integration on matlab

  - by user648666

  I'd like some help please I really need to solve this problem. Well before anything thank you for your time... My problem: I have a matrix (826x826 double) and I want to integrate this matrix with respect to a vector of (826x1 double) I don't have the functions of any of this. Is there a command or an algorithm to take the integral of a matrix with respect to a vector? Please I really need help, I'm such a newbie at matlab. Sincerely. George

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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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• Can C++ Constructors be templates?

  - by Gokul

  Hi, I have non-template class with a templatized constructor. This code compiles for me. But i remember that somewhere i have referred that constructors cannot be templates. Can someone explain whether this is a valid usage? typedef double Vector; //enum Method {A, B, C, D, E, F}; struct A {}; class Butcher { public: template <class Method> Butcher(Method); private: Vector a, b, c; }; template <> Butcher::Butcher(struct A) : a(2), b(4), c(2) { // a = 0.5, 1; // b = -1, 1, 3, 2; // c = 0, 1; } Thanks, Gokul.

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• Send a variable on the heap to another thread

  - by user1201889

  I have a strange problem in C++. An address of a Boolean gets "destroyed" but it doesn't get touched. I know that there are beater way's to accomplish what I try to do, but I want to know what I do wrong. I have a main class; this main class contains a vector of another class. There is a strange problem when a new instance gets created of this object. This is how my code works: There will start a thread when the constructor gets called of the “2nd”object. This thread gets as Parameter a struct. This is the struct: struct KeyPressData { vector<bool> *AutoPressStatus; vector<int> *AutoPressTime; bool * Destroy; bool * Ready; }; The struct gets filled in the constructor: MultiBoxClient::MultiBoxClient() { //init data DestroyThread = new bool; ReadyThread = new bool; AutoThreadData = new KeyPressData; //Reseting data *DestroyThread = false; *ReadyThread = false; //KeyPressData configurating AutoThreadData->AutoPressStatus = &AutoPressStatus; AutoThreadData->AutoPressTime = &AutoPressTime; AutoThreadData->Destroy = DestroyThread; AutoThreadData->Ready = ReadyThread; //Start the keypress thread CreateThread(NULL,NULL,(LPTHREAD_START_ROUTINE)AutoKeyThread,AutoThreadData,NULL,NULL); } As long as the constructor is running will the program run fine. But when the constructor closes the address of the “AutoThreadData-Destroy” will get corrupted. The program will crash when I call the value of the pointer. void WINAPI AutoKeyThread(void * ThreadData) { KeyPressData * AutoThreadData = (KeyPressData*)ThreadData; while(true) { if(*AutoThreadData->Destroy == true) //CRASH { *AutoThreadData->Ready = true; return; } Sleep(100); } } What did I test: I logged the address of the AutoThreadData and the AutoThreadData-Destroy when the constrcutor is running and clossed; the AutoThreadData address is equal to AutoThreadData when the constructor is closed. So there is no problem here. The address of AutoThreadData-Destroy gets destroyed when the constructor is closed. But how can this happen? The Boolean is on the heap and the KeyPressData struct (AutoThreadData) is on the heap. Destroy before: 00A85328 Destroy after: FEEEFEEE Can someone maby explain why this crash? I know that I can send a pointer to my class to the thread. But I want to know what goes wrong here. That way I can learn from my mistakes. Could someone help me with this problem? Thanks!

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• How is the syntax for stl iterators implemented?

  - by Liberalkid

  I've been working on writing a library in my spare time to familiarize myself more with c++ and singular value decomposition. I've been working on writing an Iterator class and I'm entirely capable of writing the functionality and I have already for my own currently MatrixIterator class. I'm guessing that it involves namespaces because: vector<int>::iterator Would appear to be an iterator from the namespace vector, but namespaces are another topic which I'm not familiar with. Mainly I'm asking what would it involve to implement an iterator such that it could be referenced in a similar way to the stl iterators. I'm also aware that I could use boost.iterators or something similar to save myself a lot of work, but I'm more interested in learning all of the details that go into something like this.

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• is there a way to use cin.getline() without having to define a char array size before hand?

  - by zebraman

  Basically my task is having to sort a bunch of strings of variable length ignoring case. I understand there is a function strcasecmp() that compares cstrings, but doesn't work on strings. Right now I'm using getline() for strings so I can just read in the strings one line at a time. I add these to a vector of strings, then convert to cstrings for each call of strcasecmp(). Instead of having to convert each string to a cstring before comparing with strcasecmp(), I was wondering if there was a way I could use cin.getline() for cstrings without having a predefined char array size. Or, would the best solution be to just read in string, convert to cstring, store in vector, then sort?

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