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  • A question on vectors, pointers and iterators

    - by xbonez
    Guys, I have a midterm examination tomorrow, and I was looking over the sample paper, and I'm not sure about this question. Any help would be appreciated. Let v be a vector<Thingie*>, so that each element v[i] contains a pointer to a Thingie. If p is a vector<Thingie*>::iterator, answer the following questions: what type is p? what type is *p? what code provides the address of the actual Thingie? what code provides the actual Thingie?

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  • Writing booleans to file

    - by Sara
    Hello, I have a piece of code that gives a runtime error. Can anyone help find out why? vector<int> intData; vector<bool> boolData; for(int i=0;i<19000;i++) boolData.push_back(false); string ofile = "tree.dat"; ofstream fout(ofile.c_str(),ios::out | ios::binary); if (!boolData.empty()) fout.write((char *)&boolData[0], sizeof(bool)*boolData.size()); fout.close(); It gives the error when it tries to write the file (fout.write).

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  • numpy array C api

    - by wiso
    I have a C++ function returning a std::vector and I want to use it in python, so I'm using the C numpy api: static PyObject * py_integrate(PyObject *self, PyObject *args){ ... std::vector<double> integral; cpp_function(integral); // this change integral npy_intp size = {integral.size()}; PyObject *out = PyArray_SimpleNewFromData(1, &size, NPY_DOUBLE, &(integral[0])); return out; } when I call it from python, if I do import matplotlib.pyplot as plt a = py_integrate(parameters) print a fig = plt.figure() ax = fig.add_subplot(111) ax.plot(a) print a the first print is ok, the values are correct, but when I plot a they are not, and in particular in the second print I see very strange values like 1E-308 1E-308 ... or 0 0 0 ... as an unitialized memory. I don't understand why the first print is ok.

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  • Android: How to invalidate multiple parts of screen

    - by user342731
    I need to be able to selectively invalidate multiple (about 20) rectangles on the screen for performance reasons, so tried the following: Vector<Rect> myRects = new Vector<Rect>(); // ... add some Rects to myRects for (Rect r : myRects) { invalidate(r); } However this seems to invalidates a union of all the Rect's, forming one large rectangle which covers all of small ones I'm trying to invalidate. How can one invalidate multiple areas on the screen, and only those areas?

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  • How would you go about tackling this problem? [SOLVED in C++]

    - by incrediman
    Intro: EDIT: See solution at the bottom of this question (c++) I have a programming contest coming up in about half a week, and I've been prepping :) I found a bunch of questions from this canadian competition, they're great practice: http://cemc.math.uwaterloo.ca/contests/computing/2009/stage2/day1.pdf I'm looking at problem B ("Dinner"). Any idea where to start? I can't really think of anything besides the naive approach (ie. trying all permutations) which would take too long to be a valid answer. Btw, the language there says c++ and pascal I think, but i don't care what language you use - I mean really all I want is a hint as to the direction I should proceed in, and perhpas a short explanation to go along with it. It feels like I'm missing something obvious... Of course extended speculation is more than welcome, but I just wanted to clarify that I'm not looking for a full solution here :) Short version of the question: You have a binary string N of length 1-100 (in the question they use H's and G's instead of one's and 0's). You must remove all of the digits from it, in the least number of steps possible. In each step you may remove any number of adjacent digits so long as they are the same. That is, in each step you can remove any number of adjacent G's, or any number of adjacent H's, but you can't remove H's and G's in one step. Example: HHHGHHGHH Solution to the example: 1. HHGGHH (remove middle Hs) 2. HHHH (remove middle Gs) 3. Done (remove Hs) -->Would return '3' as the answer. Note that there can also be a limit placed on how large adjacent groups have to be when you remove them. For example it might say '2', and then you can't remove single digits (you'd have to remove pairs or larger groups at a time). Solution I took Mark Harrison's main algorithm, and Paradigm's grouping idea and used them to create the solution below. You can try it out on the official test cases if you want. //B.cpp //include debug messages? #define DEBUG false #include <iostream> #include <stdio.h> #include <vector> using namespace std; #define FOR(i,n) for (int i=0;i<n;i++) #define FROM(i,s,n) for (int i=s;i<n;i++) #define H 'H' #define G 'G' class String{ public: int num; char type; String(){ type=H; num=0; } String(char type){ this->type=type; num=1; } }; //n is the number of bits originally in the line //k is the minimum number of people you can remove at a time //moves is the counter used to determine how many moves we've made so far int n, k, moves; int main(){ /*Input from File*/ scanf("%d %d",&n,&k); char * buffer = new char[200]; scanf("%s",buffer); /*Process input into a vector*/ //the 'line' is a vector of 'String's (essentially contigious groups of identical 'bits') vector<String> line; line.push_back(String()); FOR(i,n){ //if the last String is of the correct type, simply increment its count if (line.back().type==buffer[i]) line.back().num++; //if the last String is of the wrong type but has a 0 count, correct its type and set its count to 1 else if (line.back().num==0){ line.back().type=buffer[i]; line.back().num=1; } //otherwise this is the beginning of a new group, so create the new group at the back with the correct type, and a count of 1 else{ line.push_back(String(buffer[i])); } } /*Geedily remove groups until there are at most two groups left*/ moves=0; int I;//the position of the best group to remove int bestNum;//the size of the newly connected group the removal of group I will create while (line.size()>2){ /*START DEBUG*/ if (DEBUG){ cout<<"\n"<<moves<<"\n----\n"; FOR(i,line.size()) printf("%d %c \n",line[i].num,line[i].type); cout<<"----\n"; } /*END DEBUG*/ I=1; bestNum=-1; FROM(i,1,line.size()-1){ if (line[i-1].num+line[i+1].num>bestNum && line[i].num>=k){ bestNum=line[i-1].num+line[i+1].num; I=i; } } //remove the chosen group, thus merging the two adjacent groups line[I-1].num+=line[I+1].num; line.erase(line.begin()+I);line.erase(line.begin()+I); moves++; } /*START DEBUG*/ if (DEBUG){ cout<<"\n"<<moves<<"\n----\n"; FOR(i,line.size()) printf("%d %c \n",line[i].num,line[i].type); cout<<"----\n"; cout<<"\n\nFinal Answer: "; } /*END DEBUG*/ /*Attempt the removal of the last two groups, and output the final result*/ if (line.size()==2 && line[0].num>=k && line[1].num>=k) cout<<moves+2;//success else if (line.size()==1 && line[0].num>=k) cout<<moves+1;//success else cout<<-1;//not everyone could dine. /*START DEBUG*/ if (DEBUG){ cout<<" moves."; } /*END DEBUG*/ }

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  • Webservice and ORM Framework?

    - by Sebastian
    Does anybody know a good web framework that includes an ORM mapper and allows straight forward implementation of web services? I'm looking for a framework written in PHP or C++. I'm looking for the following features (not all of them required, some will do nicely) data definition in one place used by database and web service WSDL generation XML output/JSON output boilerplate code generation So what I would like is a framework that let's me specify the objects, the web service functions on those objects and then generate everything that is required leaving me to fill the business logic (connecting the database to the web service). Anything like that out there? Background information for why I need this: I'm looking into creating a web project: the client is a rich web application that fetches all its data using AJAX. It will be completely custom made using only a low level javascript library. The server back end is supposed to serve static content and javascript (basically the rich web application) and to provide a RESTful web service API (which I would like to implement using aforementioned framework).

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  • add Component to JPanel

    - by jouzef19
    Hi , I am using netBeans editor to create desktop application . and i want to add Component without using drag and drop way. I am trying code like this for adding JList to JPanel but nothing showed JList jl = new JList(); Vector<String> v= new Vector<String>(); v.add("one"); v.add("Two"); v.add("Three"); jl.setListData(v); JScrollPane js = new JScrollPane(jl); js.setLocation(50, 50); js.setSize(100, 100); js.setVisible(true); jPanel1.add(js);

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  • C++ using cdb_read returns extra characters on some reads

    - by Moe Be
    Hi All, I am using the following function to loop through a couple of open CDB hash tables. Sometimes the value for a given key is returned along with an additional character (specifically a CTRL-P (a DLE character/0x16/0o020)). I have checked the cdb key/value pairs with a couple of different utilities and none of them show any additional characters appended to the values. I get the character if I use cdb_read() or cdb_getdata() (the commented out code below). If I had to guess I would say I am doing something wrong with the buffer I create to get the result from the cdb functions. Any advice or assistance is greatly appreciated. char* HashReducer::getValueFromDb(const string &id, vector <struct cdb *> &myHashFiles) { unsigned char hex_value[BUFSIZ]; size_t hex_len; //construct a real hex (not ascii-hex) value to use for database lookups atoh(id,hex_value,&hex_len); char *value = NULL; vector <struct cdb *>::iterator my_iter = myHashFiles.begin(); vector <struct cdb *>::iterator my_end = myHashFiles.end(); try { //while there are more databases to search and we have not found a match for(; my_iter != my_end && !value ; my_iter++) { //cerr << "\n looking for this MD5:" << id << " hex(" << hex_value << ") \n"; if (cdb_find(*my_iter, hex_value, hex_len)){ //cerr << "\n\nI found the key " << id << " and it is " << cdb_datalen(*my_iter) << " long\n\n"; value = (char *)malloc(cdb_datalen(*my_iter)); cdb_read(*my_iter,value,cdb_datalen(*my_iter),cdb_datapos(*my_iter)); //value = (char *)cdb_getdata(*my_iter); //cerr << "\n\nThe value is:" << value << " len is:" << strlen(value)<< "\n\n"; }; } } catch (...){} return value; }

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  • Cuda program results are always zero in HW, correct in EMU??

    - by Orion Nebula
    Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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  • STL member variable initalization issue with windows API

    - by Django
    I am creating a windows app that uses a vector of stings as a member variable. For some reason, I can compile but when it tries to get at any of the vectors members is crashes. the error is 0xC0000005: Access violation reading location 0xcdcdcdd9. in the member function of the vector class. this is the size() function where it breaks. size_type capacity() const { // return current length of allocated storage return (this->_Myend - this->_Myfirst); } I am using visual studios 2010. thank you Django

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  • Why won't this compile and how can it be implemented so that it does?

    - by George Edison
    Here is some C++ code I'm playing around with: #include <iostream> #include <vector> #define IN , #define FOREACH(x,y) for(unsigned int i=0;i<y.size();i++) { x=y[i]; #define ENDFOREACH } using namespace std; int main() { vector<int> ints; ints.push_back(3); ints.push_back(4); ints.push_back(5); ints.push_back(6); FOREACH(int item IN ints) cout << item; ENDFOREACH return 0; } However, I get an error: macro "FOREACH" requires 2 arguments, but only 1 given The code compiles if I change the IN to a comma. How can I get the IN to take the place of a comma?

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  • Type parameterization in Scala

    - by horatius83
    So I'm learning Scala at the moment, and I'm trying to create an abstract vector class with a vector-space of 3 (x,y,z coordinates). I'm trying to add two of these vectors together with the following code: package math class Vector3[T](ax:T,ay:T,az:T) { def x = ax def y = ay def z = az override def toString = "<"+x+", "+y+", "+z+">" def add(that: Vector3[T]) = new Vector3(x+that.x, y+that.y, z+that.z) } The problem is I keep getting this error: error: type mismatch; found : T required: String def add(that: Vector3[T]) = new Vector3(x+that.x, y+that.y, z+that.z) I've tried commenting out the "toString" method above, but that doesn't seem to have any effect. Can anyone tell me what I'm doing wrong?

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  • C++: Trouble with Pointers, loop variables, and structs

    - by Rosarch
    Consider the following example: #include <iostream> #include <sstream> #include <vector> #include <wchar.h> #include <stdlib.h> using namespace std; struct odp { int f; wchar_t* pstr; }; int main() { vector<odp> vec; ostringstream ss; wchar_t base[5]; wcscpy_s(base, L"1234"); for (int i = 0; i < 4; i++) { odp foo; foo.f = i; wchar_t loopStr[1]; foo.pstr = loopStr; // wchar_t* = wchar_t ? Why does this work? foo.pstr[0] = base[i]; vec.push_back(foo); } for (vector<odp>::iterator iter = vec.begin(); iter != vec.end(); iter++) { cout << "Vec contains: " << iter->f << ", " << *(iter->pstr) << endl; } } This produces: Vec contains: 0, 52 Vec contains: 1, 52 Vec contains: 2, 52 Vec contains: 3, 52 I would hope that each time, iter->f and iter->pstr would yield a different result. Unfortunately, iter->pstr is always the same. My suspicion is that each time through the loop, a new loopStr is created. Instead of copying it into the struct, I'm only copying a pointer. The location that the pointer writes to is getting overwritten. How can I avoid this? Is it possible to solve this problem without allocating memory on the heap?

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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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  • Closure and nested lambdas in C++0x

    - by DanDan
    Using C++0x, how do I capture a variable when I have a lambda within a lambda? For example: std::vector<int> c1; int v = 10; <--- I want to capture this variable std::for_each( c1.begin(), c1.end(), [v](int num) <--- This is fine... { std::vector<int> c2; std::for_each( c2.begin(), c2.end(), [v](int num) <--- error on this line, how do I recapture v? { // Do something }); });

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  • How can I use STL sort in c++ to sort some values in the class?

    - by Morteza M.
    I have a class named Graph, in this class I have a member named V, it is a vector. I have a struct named Edge, and a list of Edges. like below: struct Edge{ int u; int v; Edge(int u,int v){ this-u=u; this-v=v; } }; class Graph{ vector < Vertex > V; . . . int edgeCmp(Edge* x,Edge* y){ return (V[x-v].dv].d)?1:0; } void someFunction(){ list backEdges; backEdges.sort(&Graph::edgeCmp); } } But it doesn't work!! may someone help me to do such a thing?

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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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  • passing a class method as opposed to a function in std::sort

    - by memC
    hi, Within a class, I am trying to sort a vector, by passing a method of the same class. But it gives errors at the time of compilation. Can anyone tell what the problem is? Thank you! it gives the following error: argument of type bool (Sorter::)(D&, D&)' does not matchbool (Sorter::*)(D&, D&)' I have also tried using sortBynumber(D const& d1, D const& d2) #include<vector> #include<stdio.h> #include<iostream> #include<algorithm> class D { public: int getNumber(); D(int val); ~D(){}; private: int num; }; D::D(int val){ num = val; }; int D::getNumber(){ return num; }; class Sorter { public: void doSorting(); bool sortByNumber(D& d1, D& d2); std::vector<D> vec_D; Sorter(); ~Sorter(){}; private: int num; }; Sorter::Sorter(){ int i; for ( i = 0; i < 10; i++){ vec_D.push_back(D(i)); } }; bool Sorter::sortByNumber(D& d1, D& d2){ return d1.getNumber() < d2.getNumber(); }; void Sorter::doSorting(){ std::sort(vec_D.begin(), vec_D.end(), this->sortByNumber); }; int main(){ Sorter s; s.doSorting(); std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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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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  • 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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