I searching for a container/collection, that can access very fast to objects with the associated id.
Arrays are a bad idea, because it can be that I must store objects with a big id for example 9394034, so the array would be to big.
class A (abstract)
class B : A
class C {
void add ( A(&*?) a )
std::vector<std::unique_ptr<A>> data; //unique_ptr<A> because A is abstract and therefore vector<A> isn't possible
}
upper situation. What is the best way to pass add an object of class B to C?
with C::add(A* a){ vector.push_back( unique_ptr<A>(a) ); }
and
int main() {
C c;
c.add( new B() );
}
This works, but i don't think it's very nice, because you could delete the pointer in main. What happens then with the unique_ptr? I could probably make C::add( std::unique_ptr<A> u_p ); but maybe it can be avoided that the "user" (in main() ) has to create the unique_ptr itself.
I'm using mingw with gcc 4.4.1. I'm trying to write a function that operates only on unique objects that have been explicitly moved.
Code:
#include <iostream>
#include <memory>
typedef std::unique_ptr<int> unique;
void eat(unique&& i)
{
std::cout << *i << std::endl;
[Code] ....
This is confusing to me because it compiles, yet my unique i is passed by R-value reference, without ever being explicitly moved. I thought named objects could NEVER be considered R-value references... Am I wrong to think that the above is extremely dangerous? After the call to "eat", my "i" has been destroyed internally, I could save by passing by value:
Code:
#include <iostream>
#include <memory>
typedef std::unique_ptr<int> unique;
void eat(unique i) {
std::cout << *i << std::endl;
[Code] ....
But at this point, I'm paying for a (theoretically cheap) move copy, when I could be paying nothing at all... A third solution would be to overload with a const ref version, but at this point, I get an obscure linker error, when I'm really looking for a compiler error...
Code:
#include <iostream>
#include <memory>
typedef std::unique_ptr<int> unique;
void eat(const unique&);
void eat(unique&& i)
[Code] ....
I'm actually trying to write a container that manages unique objects, and was trying to write a function that accepts only moved objects.
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'm having trouble understanding on how to actually store into a container from another class. Any simple example.
View 9 Replies View RelatedI've started programming my little program called vLibrary (program I want to make for the library in my city) and after I m done with console application I will try to implement wxWidgets.My program will be able to add new users to the system, new books and new librarians.
Now, I m confused what data types to use and how to store objects (newly created users, books etc) to my program so later on they can log in the system etc. Logic of the program is completely clear to me but I m not sure how to make array of objects and store them in memory or in a certain file, how to store password and make some kind of encryption etc.which data structure from STL should I use and how.
I'm using the SDL library and trying to match the C++11 standards... Anyway, I thought about a vector where I store all the addresses of game instances, so I can access them anytime... I tried with this function:
int instance_new(std::vector<uintptr_t> &instance_id, unsigned &instance_size, Instance *pointer) {
instance_id[instance_size] = reinterpret_cast<std::uintptr_t>(pointer);
instance_size++;
instance_id.resize(instance_size);
return 0;
}
Where "Instance" is the 'parent' class of various child classes like the player. So, if I have to search the existing of a thing in my game, I should check if the address references to an instance of class. How can I do this?
So starting with the Item.h file :
#ifndef ITEMH
#define ITEMH
using namespace std;
class Item
[Code]...
I think I'm getting the wrong idea about strings. I thought I could add data just by using '+=' but apparently not.
Okay, I'm not entirely certain where my code is messed up, but when I run the console it asks if I want to add Employee information and then it just skips through everything when I say yes.
#include <iostream>
#include <iomanip>
#include <string>
[Code].....
I'm working on my first video game. So far I have a few classes in the game starting with the Game class which includes a list of GameObjects (another class). There are several classes that inherit from GameObjects used to implement things like bullets, explosions, various enemy types, etc.
The game essentially iterates through the list of GameObjects to update/render them. I would like to provide access to the Game's list of GameObjects inside another class (like the Bullet class) so I can put new objects on the list. For example, when a bullet hits, I want to add an explosion to the Game's GameObject list it can be updated/rendered.
How this should be setup? I was considering adding a pointer to the Game or GameObject list to the GameObject class (and methods to access it), but I was wondering if there is a better way to set this up?
Overview of problem : I am using std::vector to hold objects of Subject. Now this vector contains lots of objects( with lots I mean 10-20 objects at max) . These objects have string member values like category and sub_category. Both category and sub_category can have string which can be same of other objects's sub_category & category.
Issue: Now I want my std::vector to have only those objects whose's sub_category are unique. If category is not unique that's not a problem .
Secondly if we found 2 objects having same sub_category then we have to delete one of them from the vector. we will delete it based on some rules example
Rules for deleting are if
i) instance of Subject ->category = " Land " OR if category = "Jungle" then delete other duplicate object ,
ii) if above condition doesn't match then delete either of them.
I am wondering , how would I compare the sub-items from the vector . For example. I have class say Subject
class Subject {
public :
// some constructors,
// functions to get ., set category and sub category
std::String get_sub_category()
std::string get_category();
private:
std::string category;
std::string sub_category;
}
I have vector which stores object of Subjects. Example : vector<Subject> copy_vector;
Now what I want is to delete the object from vector that has same sub_category I am not looking for source code buT i need a starting point,? Example:
copy_vector[0] = Animal object that has sub_category Tiger
copy_vector [1] = Animal object with Lion as sub category
copy_vector[2] = Forest object with sub_category Tiger
What I want is to based on some conditions(which I can do ) remove either Forest or Animal object containing Tiger. But for that how would I do comparison? I have written the function and have checked it.
std::vector< Subject >copy_vector;
// copy_vector contains all the objects of Subject with redundant sub_category
for( std::vector< Subject >::iterator ii = copy_vector.begin() ; ii != copy_vector.end() ; ++ii ) {
sub_category = ii->get_sub_category();
[code] ....
I've got 2 classes, Store and Transaction and I would like to create a priority queue of objects Transaction as a variable of Store class.
My store.h
#ifndef __STORE_H_INCLUDED__
#define __STORE_H_INCLUDED__
#include <queue>
using namespace std;
#include "Transaction.h"
struct TransactionCompare;
[Code] ....
The error im getting with this set up is
error C2664: 'bool TransactionCompare::operator ()(const Transaction &,const Transaction &)
const' : cannot convert parameter 1 from 'Transaction *' to 'const Transaction &'
This has been bothering me for a while now, and I finally put together an example:
#include <iostream>
#include <string>
using namespace::std;
[Code]....
In the code above, the two classes hold pointers to each other, and that's fine but it doesn't seem right since C++ prefers to pass by reference. Yes, it can still do that (see testbox and testball) but even that seems odd to me because still you need to use pointer notation for the enclosed object. Am I the only one who feels this way, and should I just get over it? Or am I missing something that would allow an object to hold a reference?
I am trying to make a program which reads a text file, separates the strings into words, then finally saving and counting each different word.
When I comment out the code where it is supposed to search for the same word in the table, the program doesn't work.Am I doing something wrong with strcmp or the loop? The 'break' just exits out of that 'for' loop right?
Code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define WORD_MAX 500
#define LIST_MAX 500
int main(){
int i, j, find;
[Code]...
I've used qsort to extract the unique student IDs by jumping every four because there's 80 rows of data and twenty students.
I want to make sure it's all working and there's something very strange going on. If you look at my code, when it comes to initialising the structure with the unique student IDs it will happily print them after each one has been initialised inside the for loop (which suggests to me it's obviously done it) but, however, when I want to print them again outside the for loop in another for loop as a "double-check" it goes horribly wrong, presumably they're not in there at all? If you traverse the code to the bottom you'll see my comments.
Now in my for loop, j is going to be incremented 20 times which will correspond to the #define STUDENTS 20. So imagine the array of structure db[j] , the first loop will set i and j both to zero, retrieve the first unique ID and store it in the structure. Then i is incremented by four to acces the next unique ID and then j is incremented by 1 to insert this new ID in the structure.
Code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
[Code]....
if i can use a function to use unique for my class and also i want to count how much each of them is duplicated. i mean i have (420,250,420,66,444,777,250) in my list i would like to know that 420 is duplicated 2 times and also 250. Is there a way to get this result ?
list<Patient *> ListePatient
ListePatient.unique(g_nas()); // nas is a attribute of the class patient
I have been trying to write this program that reads a file of courses and then stores only the unique courses in an array of strings.
for some reason it crashes while reading the 2nd line.
printf within the function are just for me trying to trace the problem.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char** uniqueCourses(FILE *fp, int *wordCount);
int main()
[code].....
I got all unique triplet from below code but I want to reduce its time complexity. It consist three for loop. So my question is, Is it possible to do in minimum loop that it decrease its time complexity. code will be execute in minimum time.
#include <cstdlib>
#include<iostream>
using namespace std;
void Triplet(int[], int, int);
void Triplet(int array[], int n, int sum) {
[Code] .....
Write a C++ program that reads lines of text from a file using the ifstream getline() method, tokenizes the lines into words ("tokens") using strtok(), and keeps statistics on the data in the file. Your input and output file names will be supplied to your program on the command line, which you will access using argc and argv[].
You need to count the total number of words, the number of unique words, the count of each individual word, and the number of lines. Also, remember and print the longest and shortest words in the file. If there is a tie for longest or shortest word, you may resolve the tie in any consistent manner (e.g., use either the first one or the last one found, but use the same method for both longest and shortest).
You may assume the lines comprise words (contiguous lower-case letters [a-z]) separated by spaces, terminated with a period. You may ignore the possibility of other punctuation marks, including possessives or contractions, like in "Jim's house". Lines before the last one in the file will have a newline (' ') after the period. In your data files, omit the ' ' on the last line. You may assume that the lines will be no longer than 100 characters, the individual words will be no longer than 15 letters and there will be no more than 100 unique words in the file.
Read the lines from the input file, and echo-print them to the output file. After reaching end-of-file on the input file (or reading a line of length zero, which you should treat as the end of the input data), print the words with their occurrence counts, one word/count pair per line, and the collected statistics to the output file. You will also need to create other test files of your own. Also, your program must work correctly with an EMPTY input file – which has NO statistics.
Test file looks like this (exactly 4 lines, with NO NEWLINE on the last line):
the quick brown fox jumps over the lazy dog.
now is the time for all good men to come to the aid of their party.
all i want for christmas is my two front teeth.
the quick brown fox jumps over a lazy dog.
Copy and paste this into a small file for one of your tests.
Hints: Use a 2-dimensional array of char, 100 rows by 16 columns (why not 15?), to hold the unique words, and a 1-dimensional array of ints with 100 elements to hold the associated counts. For each word, scan through the occupied lines in the array for a match (use strcmp()), and if you find a match, increment the associated count, otherwise (you got past the last word), add the word to the table and set its count to 1.
The separate longest word and the shortest word need to be saved off in their own C-strings. (Why can't you just keep a pointer to them in the tokenized data?)
Remember – put NO NEWLINE at the end of the last line, or your test for end-of-file might not work correctly. (This may cause the program to read a zero-length line before seeing end-of-file.)
Here is my solution:
#include<iostream>
#include<iomanip>
#include<fstream>
using std::cout;
using std::ifstream;
using std::ofstream;
using std::endl;
using std::cin;
using std::getline;
void totalwordCount(ifstream&, ofstream&);
[Code] .....
Question: In the uniquewordCount() function, I am having trouble counting the total number of unique words and counting the number of occurrences of each word. In the shortestWord() and longestWord() function, I am having trouble printing the longest and shortest word in the file. In the countLines() function, I think I got that function correct, but it is not printing the total number of lines. Is there anything that I need to fix in those functions?
Is there a way of using a rand-function in a way that it seeds the same random numbers every time the function is used? I'm looking fomr something like:
int * randfunction(hash maybe){
//Fancy code...
return // quasi random numbers, same each time function is used.
}
I'm testing an algorithm where I need a set of unique random numbers. So far I've only used hard coded numbers on small scale test runs. I'd like to do the up scaling, but haven't really figured out how to seed random numbers like I need to.
I'm working on a list of functions that can create a unique ID for a computer. Here's what i have so far:
GetAdapterInfo();
RegOpenKeyEx();
GetVolumeInformation():
CoCreateGUID();
Are there any other functions that do this?
I have a dataset which is a coauthorship network (a .txt file).I want to replace all the names of the authors with a unique number(no matter what the number is but it's important these numbers should be unique).
I've opened the dataset in excel then copy the author's names to another excel file,then I want to replace the authors names with their row numbers. what should i do?
bool isUnique(string _str)
{
bool char_set[256];
int len = _str.length();
memset(char_set, '/0', 256);
for(int i = 0; i < len; ++i)
[Code] .....
I came across this code to find if string has unique characters...i didnt understand why they subracted ascii value of character '0' in the statement int val = _str[i]- '0' and what is happening with the statements...
if(char_set[val])
{
return false;
}
char_set[val] = true;
I take each character in the sting and traverse the whole string .and if count is 2 i use break and conclude that its not unique and not otherwise...can i use this method or this is not efficient????
Would there be anyway for the compiler, or the language, to provide a unique ID during compilation?
I've been using UUID generators, but I've always found the approach of copy pasting from a program to code to be kind of... limiting. If I want a random number, can't the compiler guarantee this for me?
It already does the same thing for anonymous namespaces, so...
I've been studying metaprogramming and reviewing many documents and code regarding boost files. What I've been trying to understand and accomplish is creating various types using typedef, template and struct, similar to that of the boost files themselves, to create comparators. Ultimately, I want to be able to create a type that has sub-properties which can be further compared and classified.
Informal example:
create type
typedef int coordinate[3];
create standards - "typeless prototypes"
static const coordinate _x = {1,0,0};
static const coordinate _y = {0,1,0};
static const coordinate _z = {0,0,1};
We "now have" three variables under one unique type. Now I want to wrap this further to work with other types (int, float, etc.).
create special cases
template<class ty, coordinate c> struct coord_type;
typedef coord_type<int,x> x_i;
typedef coord_type<float,x> x_f;
typedef coord_type<int,y> y_i;
typedef coord_type<float,y> y_f;
typedef coord_type<int,z> z_i;
typedef coord_type<float,z> z_f;
declare more standards
const x_i i_i;
const x_f i_f;
const y_i j_i;
const y_f j_f;
const z_i k_i;
const z_f k_f;
Where other variables can be represented based off this i,j,k standard and written in a more direct vector form.
And so on...
What I essentially would like to do is have x,y,z variables act as standards for an i,j,k system that classify arbitrary variables of the coordinate type: Is the arbitrary variable i, j, or k? Is it defined as an int or float type?
Where arguments such as sum_y = var1 + var2; are valid, provided:
sum_y is outputted as 6j, and var1 and var2 are 2j and 4j, respectively.
Here is what I'm trying to accomplish (it is a rather simple program): A classroom of students are to grade a certain number of other exams. The exams should be distributed equally and RANDOMLY, every student should receive the same number of exams, and no student should receive their own exam to grade. The only problem I have is to generate unique random exams for each student. Right now, I have it set to where each exam is distributed the same number of times, every student gets the same number of exams to grade, and no one gets there own. However, I don't have any parameters that prevent one student from getting the same exam multiple time.
Here is an example output:
Student 1 will grade: 4 3 2 5 <- CORRECT OUTPUT (no exam appears more than once)
Student 2 will grade: 5 5 5 1 <- exam 5 appears three times
Student 3 will grade: 4 2 2 2 <- exam 2 appears three times
Student 4 will grade: 3 3 1 1 <- exams 3 and 1 each appear twice
Student 5 will grade: 1 3 4 4 <- exam 4 appears twice
(each exam appears four times and every student is assigned four exams. no one gets their own)
Here is my code (area of problem is close to the bottom):
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void create_class (int);
int main (void) {
srand(time(NULL));
[Code] ....
I tried keeping the exams for each student in the array exam and then checking each one every time I generate a number, but that didn't work.