C++ :: Custom STL Compatible Containers And Iterators?
Jul 18, 2012
So i made an STL compatible container.And to make this work I had to make my own iterator (derived from std::iterator).
What is the portable (if any) and "well behaved" thing to do in case of usage anomalies.such as iterating an iterator too far, or passing an invalid index to a operator[]
Looking at how VC++ does things in something like std::array or std::vector.
Code:
iterator_type& operator+=(difference_type offset)
{// increment by integer
#if _ITERATOR_DEBUG_LEVEL == 2
if (size < index + offset)
{// report error
[Code] .....
lots of names starting with underscores, so it's implementation specific. Is there even a "well behaved" thing to do ? Or is any such work always going to be compiler specific?
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Jul 5, 2012
I'm working on writing some classes around a ROM hardware addon card. The classes expose the data on the ROM as a container with iterators, much like a vector or a list.
The classes don't have any data themselves, since all the data is on the ROM.
I'm having some dillemma's as to how to approach/implement the classes. If you were to write somethign like this... Or were using something like this written by someone else.... How would you expect this to be done ?
1) Make all the member functions static, make a private constructor to prevent making instances. This works, but may look a bit weird...
Code:
for (auto it = RomTable::begin(); it != RomTable::end(); ++it)
2) expect users to make a (dummy) instance, then use it as a regular container. this might be a bit counter intuitive since the class has no datamembers.
3) create a single instance, expect users to use that everywhere. make the constructor inaccessible. Some C++ 'purists' might perceive this as global data and thus not a good solution ?
Additionally. Do I need to provide both a const_iterator and an iterator ? There's nothing to be modified, so I'm guessing an iterator isn't needed (?) Or will some STL stuff not work without an iterator ? I'm obviously not fussed about the STL functions that make changes to the container to not work (like sort, fill, swap...)
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Feb 28, 2015
after having my previous thread removed due the project I was working on being usable for malicious purposes I was directed to the project suggestions page; from there I decided to go ahead with an FTP client. I am now looking into how I will go about this and it is looking very simple (too simple maybe I am missing something? ). I was wondering if the standard FTP web requests in the standard library will work with programs such as FileZilla. As far as I can think everything should follow the same standard but I just wanted to make sure. I will be setting up an FTP server on my PC with FileZilla if so and getting to work tonight!
Also, off topic questions; is it generally considered bad practice to include a lot of logical code in a Form class? I generally try to make other classes contain all my logic code no matter how small (such as connecting to a socket, or writing to files) but I often see people's personal projects have nearly all of their code thrown into the same class as a Form.
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Mar 11, 2014
I am looking for UUID 64 bit compatible library. I have used BOOST UUID generator, but faced compatibility issues with stlport4 and iostream libraries compiling together.
Any other such UUID generator working on similar concepts that of BOOST UUID library!
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Aug 10, 2014
This code compiles in release mode but I get this compile error in debug mode:
Error1error C2664: 'GetPrivateProfileStringA' : cannot convert parameter 4 from 'wchar_t [255]' to 'LPSTR'g:easywebstoreuploaderini.cpp45
Code:
CString CIniFile::getKeyValue(CString strKey, CString strSection) {
wchar_t ac_Result[255];
// Get the info from the .ini file
m_lRetValue = GetPrivateProfileString(strSection, strKey, _T(""), ac_Result, 255, m_strFileName);
CString strResult(ac_Result);
return strResult;
}
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Feb 21, 2014
I've been working on a project that involves storing pointers to dynamically allocated class objects in an STL list, but trying to run it something's going wrong.
list<Actor*>::iterator it;
for(it = m_actors.begin() ; it != m_actors.end() ; ++it)
{
delete *it;
[Code]....
But it seems like that has a memory leak. Does pop_front() just call the destructor for the object, or will it delete a dynamically allocated chunk of memory? If not, how can I do that deletion to avoid a memory leak?
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Feb 14, 2015
Im trying to create a function that searches my array for a specific string, and then displays that string and the other content associated with it. I'm basically searching for a keyword within an array that has multiple strings with in each element.
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Jul 1, 2012
I need to create function Sum() that calculates sum between two containers. Code below work fine except function Sum between two containers...
How I should re - write my code that everything work fine.
Condition of exercise is : "Also create a Sum() function that calculates the sum between two iterators. The function then uses the template argument for the iterator type and accepts two iterators, the start- and end iterator"
1>------ Build started: Project: HP2_ex2_iter, Configuration: Debug Win32 ------
1> main.cpp
1>c:all myс++ha level 7solutionlevel 7 homework overview of the standard template libraryhp2_ex2_itermain.cpp(47): error C2275: 'C1' : illegal use of this type as an expression
[Code]...
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Oct 27, 2012
I have a situation where I have two identical storage containers:
Code:
////////////// multiplatform version
union _SOVector3 {
struct { float x, y, z; };
struct { float r, g, b; };
float v[3];
[Code] .....
SOVector3 is part of a namespace with specialized functions that are generic and intended for multiplatform usage.
GLKVector3 is dedicated to the Mac and has its own set of functions.
But what I want to do is freely interchange the storage between these two namespaces. Such as like this:
Code:
start = clock();
SOVector4 myVec4 = SOVector4Make(1.0f, 3.0, 6.0f, 1.0);
SOMatrix4 myMat4 = SOMatrix4Identity;
for (uint i=0; i<100000; ++i ) {
[Code] ....
But I am getting errors when I typecast this.
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Dec 25, 2014
I'm having problem getting the values for iterators. This code:
auto sum = inputVec.begin() + itLast;
gave this error: no match for 'operator+'
#include <iostream>
#include <vector>
#include <iterator>
using namespace std;
int main(){
vector<int> inputVec;
[Code] .....
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Jun 25, 2013
#include <iostream>
#include <vector>
using namespace std;
int main() {
int * ptr;
vector<int> data;
data.resize( 1000 );
[Code] ....
So I need container that doesn't rellocate their address, It doesn't need to be like vector that everything is in a single pointer such as
int * a = new int[2000];
I have a pointer pointing to a member of a container and it needs to remain valid... doing
vector<int *> Array;
// allocating
for( int i = 0; i < 1000; ++ i ){
Code] ...
Waste of time, allocating them and deallocate them seem to take some time too
a List is also not efficient enough because I access them based on index
It is not a int it is pointing to but a texture, for the sake of simpler example I pick int
So is there a container that doesn't change member address and allocate when it needs to expand ?
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Mar 5, 2013
I need manipulating a set of containers. I created a vector that contained vectors of objects:
std::vector< std::vector<Terrain> > mapArray(num1, std::vector<Terrain>(num2));
where num1 and num2 are arbitrary numbers. and Terrain is the class of objects I'm trying to store.
I want to be able to use push_back on both the main vector and the vectors within the mapArray vector but I'm unsure of how to target the inner vectors with push_back. How to dynamically store a 2D array of objects.
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Feb 6, 2013
Do stream iterators, such as std::istreambuf_iterator<char>, read a chunk of bytes internally, or do they read the stream one byte at a time?
Because I am thinking to write a BufferedFile class which uses an std::vector<char>.
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May 20, 2013
In this code:
vector<int> mydata(100);
mydata[2] = 999;
In statement 2 does that call the iterator to access the 3rd position and set its value to 999?
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Oct 13, 2013
Assuming I have a list of pointers to a generic type T:
#include <vector>
//...
list<T*> myList;
Now assuming I want to go on the list, and if T's type is matched to the type I'm looking for, then cast it to this type and do something. List shown here:
list<T*>:: const_iterator iter= myList.begin();
for(; iter!=myList.end(); ++iter){
if( typeid(*iter)==typeid(Something*)) //RUN-TIME ERROR
dynamic_cast<Something*>(*iter)->DoSomething();
}
how do I fix this run-time error?
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Jun 15, 2014
When using an iterator with a std container (list / vector etc) sometimes it's possible to modify the container (e.g. delete an item) yet still carry on using the iterator - whereas in other cases, modifying the container immediately invalidates any open iterators on it. Is there an easy way to know which containers fall into which category? (or does it vary from one compiler to another?)
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Oct 16, 2013
I am looking for direction on what topic I should be reading up on. I am new to C++ and Windows MFC.
This is my real world problem, in the context of the application user. (these term do not refer to OPP concepts)
I want to create shapes (containers) in an application that will respond and collect other objects;
Imagine a Windows frame, containing several 2 dimensional squares. I want to be able to drag and drop marbles into the squares,and have the square retain and display the marbles in the square, in the order that they were dropped in.
How do I create the shapes, and how will the square sense when a marble is over it?
How would I create irregular shapes (a combination of lines and curves) that would be responsive to the marbles?
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Mar 14, 2012
Suppose I'm writing a program designed to simulate a large company. I'm interested in tracking each company employee by the location where they work. This company has perhaps a thousand different locations:
class Employee {
public:
AccessorFunction1(); // does something
AccessorFunction2(); // does something different
AccessorFunction3(); // does something completely different
protected:
// Some data
[code]....
Once employees are created and pointers to them are saved in the proper Location vector, I write an accessor function, OrganizeLocation(), designed to do a number of operations on a given vector. The problem is, I have maybe a thousand vectors. How do I call this function and specify which vector I want?
Currently, I'm using this clunky solution:
void Company::OrganizeLocation(int a){
switch(a) {
case 1: {
for(unsigned int i=0; i<LocationA.size(); i++) {
LocationA[i]->AccessorFunction1();
LocationA[i]->AccessorFunction2();
LocationA[i]->AccessorFunction3();
[code]....
The key point here is that whichever vector I choose to operate upon, I'll do the exact same procedure every time. I hate this solution because it results in very long and repetitive code not to mention its very error-prone when you re-editing all those "LocationA 's into "LocationB/C/D/etc."
void Company::OrganizeLocation( string $WhichOne$ ){
for(unsigned int i=0; i<LocationA.size(); i++) {
Location$WhichOne$[i]->AccessorFunction1();
Location$WhichOne$[i]->AccessorFunction2();
Location$WhichOne$[i]->AccessorFunction3();
}
Or, if it can't be done in C++, is there a better design approach? Ultimately I need the Company object to hold multiple vectors but use one compact accessor function to perform operations on just one of them.
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Oct 8, 2014
I am working on very large code.
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Oct 9, 2014
I am working on very large code. I got a segmentation fault when trying to use one cpp file and tried to locate the error using Valgrind
Since the code is very large, I will only post a short portion of it below. I think the problem may come because triann is a vector defined in the header class, so triann[tri] is causing problems?
void ADe::aNe(int v, set<int> &nei)
{
for(set<int>::iterator iter = vert2tri[v].begin(); iter != vert2tri[v].end(); iter++)
{
[Code].....
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May 29, 2013
I have a 'Graph' class, which has derived classes for Adjacency Matrix and Adjacency List representations.
How do I provide iterators for traversing vertices and edges, when the iterator classes would have different implementations for the different derived classes ?
The following way is the only one I can think of, but seems quite cumbersome.
Code:
class Base {
public:
class BaseIterator {
};
virtual const BaseIterator& begin();
virtual const BaseIterator& end();
[Code] .....
Or is there a pattern for doing this that I'm not aware of ? Would composition be a better idea here compared to polymorphism ? I mean, I can think like..a Graph can 'have' several representation 'objects' within it.
All the involved classes are templates,not sure if that makes the situation different.
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Jul 11, 2013
I get this error when i try to run this code for an inventory in debug mode in VS. But for some reason it works just fine in release mode.
void Push_Back_Item(Item *item){
for(int y = 0; y < InvSizeY; y ++)
for(int x = 0; x < InvSizeX; x ++){
auto Iter = ItemList.find(std::make_pair(x,y));
if(Iter != ItemList.end()){
item->SetDead(); // ERROR
}
}
}
This isnt the full code though but it still gives me the same error.
The only thing "item->SetDead()" does is to set a bool to true.
This is the map i get the iterator from
std::map<std::pair<int,int>,Item*> ItemList;
This have been bugging me for quite some time now.
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Feb 7, 2014
I'm trying to write a custom allocator that I can use with the STL. Here's what I have so far :
Code:
#include <cstddef>
#include <iostream>
#include <memory>
#include <vector>
template<class T>
struct customallocator {
[Code].....
I'm doing and currently, my push_back doesn't seem to do anything.
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Oct 9, 2014
Let's say we have a custom Vector class and I need to know which of the following is considered to be more efficient and why of course.
Vector Vector::operator+(const Vector &b) const {
return Vector(x+b.x,y+b.y);
}
Vector Vector::operator+(const Vector &b) const {
Vector tmp(x+b.x,y+b.y);
return tmp;
}
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Oct 8, 2013
I've written a doubly linked list per my assignment instructions. I've implemented begin() and end() iterators for it, and they work with no problems when traversing the list. However, I need to sort the elements in the list. We are allowed to use the sort function defined in the <algorithm> header since we haven't yet covered sorting algorithms.
But, I'm running into a ton of problems. I figured as long as the begin() and end() iterators were defined for the list, then sort(list.begin(), list.end(), compare) would do the trick. The main errors I'm getting are:
error: no type named iterator_category
error: no type named value_type
error: no type named difference_type
error: no type named pointer
error: no type named reference
And also errors for no match of the + and - operators for the iterator class.
I understand reference, pointer, and value_type, but I have no idea about iterator_category and difference_type. Additionally, I'm a little unsure why the + and - operators need to be overloaded.
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Jul 13, 2014
I have a POPUP
MAIN_MENU MENU {
POPUP "&Manager" {
MENUITEM "New Royal Python", MENU_NEW_ROYAL_PYTHON
POPUP "&Select Python" {
}
}
}
I basically want to give the POPUP an ID so I can talk with it but it does not seem to be accepting a second parameter. Once I have done that I need to send a message to it to ask it to add a new item, what are the messages I need to send for this?
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