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?
Suppose you have defined a container of elements and you want do define a comparison function between elements based on the ordering of the elements in that container. What algorithm for the comparison would be the most efficient?
Example:
master = {tom, sam, mary, sally, bert, frank}
subset = {bert, sam, mary, tom}
goal: change subset to {tom, sam, mary, bert}
My current idea is to simply iterate from the beginning of the container, and whichever of the two elements is found first is the lesser (assuming the second is not the same as the first). It seems kind of naïve though. Any better performing algorithm? This is what I have so far:
#include <iostream>
#include <iterator>
#include <list>
#include <vector>
#include <stdexcept>
#include <algorithm>
[code]....
Would perhaps forcing the container to have a random access iterator, like vector, and then writing a specialized comparison function based on that perform even faster? Or perhaps force the container to be a map to integers, and compare the elements by comparing the integer mapped values?
My program gets user input and compares it against an array of characters (guessLetters[x]) to decide whether the do/while loop repeats. The whole character array contains underscores yet if i enter any letter it goes into the if statement and repeats the do/while loop.
do {
repeatflag = false;
cin >> UserInput;
UserInput = toupper(UserInput);
[Code] .....
Right now my application database is stored in the AppDataRoamingAppName directory.
The client has requested that the administrator choose the location for the database, and have a choice between a local machine, or an online repository.
The clients are not IT people, they are business people, and I don't think it's a good idea to let a user choose where to keep the central app database. Other users (think admin vs user) will need to download the database for use on their own local machines, which is how the issue even came up, it's kind of a shared database that only the admin can add to.
My compromise was to COPY the main database to the location of the user's choosing, then push updates to it as the main database was written to.
So after working on this today, I have the user choose a directory, I add the file path to the application settings, then I create the file and copy the database as needed to the new location (online repositories are next).
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.
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 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?
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?)
View 2 Replies View RelatedHow to write a program without using any type of container .
View 4 Replies View RelatedI'm having trouble understanding on how to actually store into a container from another class. Any simple example.
View 9 Replies View RelatedUnoptimized problem: I work on a table (vector of vectors). vector< vector<double> >
Optimization: If the current set of vectors is v1...vn (so each vk is a vector of double), my problem is such that I will only work on the last M of the vectors, the earlier vectors are irrelevant. I would like to reuse space to make the algorithm scalable, so I want to delete the vectors that can be forgotten. I read in a new vector, I delete the oldest vector.
Code mostly speaks for itself:
#include <list>
#include <iostream>
using namespace std;
[Code]....
I added an object of class myderiv to the container, but when I retrieve it back and try to manipulate it, it's actually of class mybase. Is there any way to keep the inheritance information in the container?
I need a container which has multiple keys. The number of keys, which are related to a value, is not constant, but it is small. (less than 10). I have tried to do this with std::map, but things are working only with a constant number of keys per value.
Something like this
key1 ----|
key2 ----|--------- value1
key3 ----|
key4 ----|--------- value2
key5 ----|
I have a class:
class Foo {
private:
MyType* things[10];
};
While I would like to overload the [] operator for the use as this:
Foo myFoo;
myFoo[0] = myFoo[1];
Right now I am getting ugly:
MyType** operator[](size_t idx) { return &(things[idx]);
//...
*(myFoo[0]) = *(myFoo[1]);
Anything to fix that up a little?