Consider a singly-linked list container.
Being constructed with an alloc<T>, it will rebind it as alloc<node<T>> for internal use.
Question: is allocator_type the same as alloc<T> or as alloc<node<T>>?
To my understanding, a Container should have an Allocator member data, which is used internally.
Question: what happens, for example, when we swap() two containers that use different allocators?
Must the allocators be swapped as well?
Must all elements of the container be reallocated when the allocator is changed?
i have two point P1 and P2 where i want to move P1 and P2 with keeping the distance and the position of the P2 relative to P1 i thought that when i keep the distance between the two point that involve keep in the same time the local position of P2 but when tested it does not work initial position of P1=(10.0f, 00.0f, 00.0f) initila position of P2 relative to p1 =(50,10,-8) we can get the global position of p2 ----- final position of P1 =(50,10,-8) final position of P2 in the world space =(40.31,8.06,-6.45) then we calculate the distance before and after we found that there are equal but when we calculate the position of p2 relative to p1 after and before we found that there are not equal.
how i can keep the local position and distance ?
how to correctly use pointers within relation to function parameters and main source file.
I noticed that char types, for example char myVariable[50]; which is an array, does not seem to require a pointer as if it already has one built in? as opposed to char *myVariable; which seems to need one - i assume this is because char has different ways to store memory in relation to pointers, because of there being multiple ways to store a string, and memory allocation as a part of that. - i stared C a few weeks ago and feel that it is difficult to progress without nailing down pointers. Also address operators provide confusion for me and written tutorials are not so clear because there are different ways to use these operators.
I have most of the code working properly, but I'm having trouble with a certain area. Currently I have multiple 2D arrays. One is a char array and the other is an int array. In the int array I have to find the max number in each column, which I've done. The problem is, I need to print the max number's row in relation to the char array's row.
For example,
Code: int array[2][3] = {60 50 30 0 100 1}
The max numbers are 60, 100, 30.
char array[2][length+1] = {nameOne nameTwo}
How it needs to print:
nameOne has max score of 60.
nameTwo has max score of 100.
nameOne has max score of 30.
I just can't understand how to compare the two arrays in the right way, so it'll know that nameOne is associated with the numbers in row 0 and nameTwo in row 1, etc.
I have a matrix class who use the stl vector to manage its
memory(UInt is typedef of size_t):
class Mtrx {
protected:
[Code]....
However, the two different classes are only different with each other on the allocator. I am thinking, that a elegant way should be merging them together.
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.
I am coding a singly-linked list container. Of course, internally it uses Node<T>.
Question: what is the correct way to use the allocator given by the user? I ask, because I've read this on the rival C++ Reference:
std::list<T, A> allocates nodes of some internal type Node<T>, using the allocator std::allocator_traits<A>::rebind_alloc<Node<T>>, which is implemented in terms of A::rebind<Node<T>>::other if A is an std::allocator
[URL]...
The above doesn't seem right to do, because then what should pointer and const_pointer be?
using pointer = std::allocator_traits<Alloc>::pointer;
using const_pointer = std::allocator_traits<Alloc>::const_pointer;
// but we're using Alloc<Node<T>> not Alloc<T>
// so maybe do this?
using pointer = value_type *;
using const_pointer = const value_type *;
I attempted to create a dynamic array class for use in my engine (due to problems regarding a dll-interface with the standard library), so I tried at making a standard-compatible allocator template class first. After I "finished" that, I went on to work on the dynamic array class itself.So I finish the dynamic array class, and test it with the standard allocator. It works perfectly, but when I test it with my custom allocator class, it fails terribly.
To make sure it wasn't my DynamicArray class that was causing issues, I tried using the custom allocator on the std::vector class template, and it didn't work either. IMy DynamicArray class code:
// Represents a dynamic array, similar to the standard library's "vector" class.
template<typename T, typename A>
class DynamicArray
{
public:
DynamicArray() :
data(nullptr),
elements(0),
capacity(0)
[code].....
The "Request" and "Free" functions are my engine's equivalent of malloc and free (or new and delete). I allocate a large buffer (16 mb), and through those functions I distribute the memory to where it's needed.
Does the requirements have changed for writing custom allocators with C++ 0x11?
A custom allocator (that uses a fixed array as its memory pool) that I have been using successfully for some time, now throws an exception!
It runs fine under VS2008 but bombs out with VS2010.
So I'm writing an RPG and I'm in need of an inventory system. Of course as an relatively old member of the forum I know best than just come here and ask so I've already researched quite a bit and I've formulated this idea.
I've kind of conceptualized it like so: I'll have some sort of STL container of a unique_ptr of my base item class. There will be derived item classes. Taking advantage of polymorphism I can then call the new Derivedclass when inserting it in the STL container.
My questions are: What STL container should be used for the inventory(fixed sized)?
What is container class? what its advantage ?
View 2 Replies View RelatedI have a pile of data, which i need to access frequently and fast. One entry consists of two unsigned ints, let`s call them source and destination.
One source can have several destinations, but this rarely ever happens. Several sources can have the same destination - this happens more frequently, but still scarcely.
Once the data is set up, it rarely ever changes - yet it should be possible to add or remove entries.
I now need to find all sources for a given destination, or all destinations for a given source.
The question: which stl container to choose?
I have tried a multimap, using the source as key. This works good for finding all d for a given s, but is inefficient in the other direction.
Do you think it would be more efficient to have two multimaps, sorted respectively by source and destination?
I am trying to come up with a way to make use of a "multilevel dynamic" container. I am parsing a file to grab some pieces of data. Lets say the first field of data I find I push into an array. At the same time lets I wish to create 2 cascaded sublevels. So an element in Modules is a pointer to the Types vector associated with that module and each element in Types is a pointer to a vector of Data. This concept should be similar to memory paging.
/*
Modules Types Data
____ _____ ______
|____|------> |_____| ---------->|______|
|____| |_____| |______|
|____| |_____| |______|
|____|
|____|
|____| _____ ______
|____|------> |_____|----------->|______|
|____| |_____| |______|
*/
Obviously this becomes very hair quickly so it is obvious that I need to dynamically create and destroy vectors (if I do it this way). Should I just create pointers using the new operator?
Here is some of my code if it is even worthwhile to read:
class Parser {
//storage arrays
vector <string> modules;
vector <string> terminal_type;
vector <string> tag_type;
vector <string> data;
[Code] ....
parse this stuff and nicely organize it.
If you take the first one, "max_logvar" is a module so everything between < and > is associated with that module.
symb is unimportant for now.
then "proterm" is a "module type" so then module now needs a module type container but I may have more than one of those.
so then I break it down by "Input" and "Output" where each of those can have the integer values (just in an array where each position will be set) that are in the fields to the right.
I have a container in c++11 and i must delete first object and i don't know how...
for (const prob& p : *static_cast<vector<prob>*>(list.listData)){
// i must delete the first object
}
How do we design a container of objects all of which belong to some subclass which directly/indirectly inherits from a given parent class? Moreover, I would like to have functions that enable me to pick only objects of a certain class type from the container.
For example if the parent class is A and I have a hierarchy of classes that derive from it, we must have a container that can contain any class that exists in this hierarchy. Also, get_B() must be able to let me examine only those objects in this container that inherit (directly/indirectly) from class B (class B exists in the hierarchy rooted at A).
Preferably, we would like to avoid downcasting. Or even explicit typechecking of any sort.
I need to create an array container with the same structure as double myA [100][100];. But I cannot declare it as array<double, 100, 100> myA; however I do need this container for its format. How can I make it work.
View 6 Replies View RelatedI know that it's a class that contains data from another class I just do not know how to make them both work together.
View 1 Replies View Relatedi built a programming language called jade that right now can only print. i want to add variables to it however. I am going to use a modified bajarne stroustrop calculator to handle expressions (ie will now include string manipulations and such), but I want to build a var class into the program to make it easier for the program. i want variables to act like python variabes, and arrays to act like python associative arrays. Ive scoured different containers, but they only work if the variable isnt an array in my language, because it will only have one type. the only thing i can come up with is a union and 4 overloaded = operators (for bool, int, double, and string) is there a better way to do this?
View 2 Replies View Relatedso i have a container called Source that is of type std::map<std::string, std::vector<std::string>> but when I try to print it with this function:
void Lexer::PrintSource()
{
for(auto Iterator = this->Source.begin(); Iterator != this->Source.end(); Iterator++)
for(auto SubIterator = Iterator->begin(); SubIterator != Iterator->end(); SubIterator++)
cout<< *SubIterator << endl;
}
i get these errors:
Lexer.cpp: In member function 'void Lexer::PrintSource()':
Lexer.cpp:29:42: error: 'struct std::pair<const std::basic_string<char>, std::vector<std::basic_string<char> > >' has no member named 'begin'
for(auto SubIterator = Iterator->begin(); SubIterator != Iterator->end(); SubIterator++)
^
Lexer.cpp:29:76: error: 'struct std::pair<const std::basic_string<char>, std::vector<std::basic_string<char> > >' has no member named 'end'
for(auto SubIterator = Iterator->begin(); SubIterator != Iterator->end(); SubIterator++)
^
I have a deposit of containers and i must delete the cats container. How i can do that?
#include <iostream>
#include <string>
#include <vector>
using namespace std;
struct Cat {
string name;
int age;
[Code] .....
I want to find all instances of a substring mysub in array container myarr and replace each occurrence of mysub with empty string " ". To do that, I'd like to use for loop with search algorithm.
Code below:
p=array iterator
for ( p=search(myarr.cbegin(),myarr.end(), mysub.begin(),mysub.end();
p!=myarr.end();
p=search(p,myarr.end(),mysub.begin(),mysub.end() ); {
[Code] ......
I need a "meaningful" way of accessing a table, the column is representing Err magnitude, and the row is representing Rate magnitude. For each error magnitude and rate magnitude, i define an action magnitude, which is the contains of the table. For example,
Code:
int matrix[10][10];
int Action1 = matrix[0][0];
int Action2 = matrix[0][1];
However, i need a better way of getting matrix[0][0], row and col itself is meaningless. I want to access the table like
"Action magnitude" = matrix["Rate magnitude 1"]["Err magnitude 2"]; using a string instead of int id.
How to easily do this in c++ container?
I have a class called CTestObject and it has one variable int id. I want to add instances of this to an std container and be able to:
1. quickly determine if the value of "int id" exists in the container and update the object
or
2. add a new object to the container
Which std container is the best for this application? What method should I use to search the container for the object id?
How do you find, when you first introduced with say some of the STL container, function or algorithms, what are its requirements? I mean,
1. what operators object should have for specific container?
2. what function args and type it should return for a algo?
3. when extending some container like with custom allocator, char_traits...and what not, what methods should be overridden? What work should they do?
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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