C++ :: Creating A Function In A Class?
Feb 16, 2014
I am currently working on a "bag" class which is sort of a common sense answer to creating a random class with difference functions. I am attempting to create a "union" function which takes two bags ie: bag1 and bag2, adds all the items in both bags and creates a new bag ie: "bag3". For some reason I keep coming up with problems instead of solutions. Maybe it's the fact I just got done with 2 days of calculus. I don't know. My code is below. Both a main(source) and header file.
Header
#ifndef BAG_H
#define BAG_H
const int BAG_CAPACITY = 20;
template <typename T>
class Bag {
private:
int count; // Number of items in the Bag
[code]....
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Jan 16, 2013
Please consider the following code :
#include <iostream>
using namespace std;
class superclass;
class subclass1;
class subclass2;
[Code] ....
As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.
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Sep 20, 2013
Suppose I have two classes A and B so how to access object of class A in constructor of B's class as a parameter.
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Aug 2, 2013
I'm currently reading the C++ Guide for Dummies
Anyway right now I'm working with pointers and classes, and when I create a new pointer for my class it looks like this...
Pen *Pointerpen = new Pen;
But in the book they threw in this...
Pen *Pointerpen = new Pen();
Can you actually designate memory space for a function? Or was this a typo on their part? It's never come up before and they didn't explain it.
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Nov 15, 2014
I was trying to implement own vector class and wrote some code. Below is the code.
Code: #include<iostream>
#include<vector>
using namespace std;
template <typename T> class MyVector
{
T *mem;
int m_size,final_size;
public:
MyVector() : final_size(1),m_size(4)
{
[code].....
I have question on this function.
Code: myVecPush_back(T t){}
Here I was able to put elements upto any number of time, but I have allocated memory to only 4 elements in T *mem.
My question, why the program is not crashing when I tried to put elements more that 4?
Is since the variable is of type Template? Any specific reason for this?
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Mar 2, 2014
I have a background in c# and am very frustrated with c++. If I created a class in c# like so:
public class Memory{
int x = 0;
int y = 0;
int height = 0;
int width = 0;
string firstname = "Bob";
string lastame = "Chester";
}
and then created a new instance of this class from a separate class by doing:
public class Main{
Memory mem = new Memory();
}
I have raked the internet for a way to create a new instance of a class in c++ while keeping its default values and have come up empty handed.
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May 16, 2013
I've just recently moved from Visual Basic 6 over to C++ and decided that I would try and write a class to mimic the Get/Set behavior seen in a variety of other programming languages. So instead of just using an overloaded function, i.e:
Code:
class NoProp {
LPCWSTR m_Title;
public:
void Title(LPCWSTR NewValue) {m_Title = NewValue;};
LPCWSTR Title() {return m_Title;};
[code].....
So far this code only works with the LPCWSTR type (const wchar_t*). Unfortunately I got to this stage using only that type, and now when I try another type, such as int, it fails. When using the int type I believe it creates an error because the constructor of InitProp expects a type of pointer to be parsed. When I try using it with int* type (the private variable then becoming int **m_Variable) it compiles, thought I cannot access the property like a normal int.
My best guess from here is that I probably have to overload the InitProp constructor in a way that it can setup the Property classes for base-types and pointer-types, and then also modify the Property class to handle both.
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May 12, 2013
I have defined a class in a header file; just the class, no templates involved. I have a program where I'm reading in data in string format. Each string consists of a word, a delimiter, and a variable name. Example:
cajun/mustard
I want to take that string and make it the variable name of that class type. It would be implemented along the lines of:
Code:
string str;
//read/process string here, get:
str = "mustard";
createName(str);
//pass string to creator function When the function is called, I should get the variable:
Class mustard;
Thing is, I'm not supposed to know beforehand what the variable names are, only that I create them as they are read in. It could be mustard, it could be Maynard_James_Keenan, it could even be bazinga.
My problem is, what do I do for createName()? I've looked into the concepts of pairing, Factory implementation, and maps, but I don't think they answer my question.
(P.S. if I run into the same variable name being read in twice, what steps can I take to make sure that a duplicate variable isn't created? Do I need to add in code, or does the compiler know to watch for multiple variables of the same name?)
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Jul 3, 2013
Creating the methods for class List
main.cpp Code: #include "List.h"
int main( )
{
List la; // create list la
la.push_front( "mom" );
la.push_back( "please" );
la.push_back( "send" );
la.push_back( "money" );
la.push_front( "hi" );
cout << "
la contains:
" << la << '
[code]...
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Oct 17, 2014
I've been given specific instructions to create an array inside a Class Matrix using a constant n. This is my class but I am getting errors. I thought that maybe I had to initialize the const and the array using the constructor function Matrix() instead of directly in the class, but I didn't have any luck with that either.
class Matrix
{
public:
Matrix();
private:
const int n=3;
int e[n][n];
};
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Sep 16, 2014
I recently posted a question related to creating a heap template class. The ultimate goal is to create a series of classes that serve a purpose that was overlooked in the Qt library that I need for my current project.
The current "end goal" is a PriorityQueue template that uses a comparer class which is inherited from a "template interface". Basically a pure virtual class template. Perhaps that is the mistake to begin with but hopefully not. (Is this a valid approach?)The problem I am getting is that when I compile the code, it says my derived comparer class is abstract.
I will include all related classes here. I doubt it is relevant but the templates and the classes based off them are in different namespaces.Here is the comparer "template interface":
// in global namespace
template<class T>
class IIMQOBJECTS_EXPORT IQComparer {
virtual int compare(T& a, T& b) = 0;
virtual bool equals(T& a, T& b) = 0;
virtual bool isGreaterThan(T& a, T& b) = 0;
virtual bool isLessThan(T& a, T& b) = 0;
};
Here is the class that is supposed to be non-abstract but isn't recognized as such:
// in the application namespace AND IN SAME project that has the NetEventInfo class
// all functions ARE defined/implemented in a cpp file
class APPCORE_EXPORT NetEventInfoComparer : ::IQComparer<NetEventInfo*> {
public:
NetEventInfoComparer();
~NetEventInfoComparer();
[code].....
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Jan 15, 2015
Let's say I reference a dll in my project that has an abstract class in it:
public abstract class Module {
public string type;
public abstract string doSomething();
}
And then I have an Assembly object, loaded from a dll that is not referenced in project, but rather loaded during run-time, containing:
public class Tester : Module
{
public static string type = "Test";
public override void doSomething() {
//Stuff being done
return "hello";
}
}
How can I get the value of "type" in the class that is loaded during runtime? How do I use the "doSomething" method of it and get the returned object?
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Mar 21, 2015
The only difficulty im having is creating a class and methods & being able to access them from my win form app. Can i get a few tips on the do's and donts of creating classes / methods and accessing them from form app.
This is what i have put together so far.
public partial class Form1 : Form {
private Image[] dicePics;
private int[] diceNum;
private Random randomize;
public Form1() {
InitializeComponent();
[code]....
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May 23, 2013
I need to create an object of a mfc derived CFormView class that's not in the doc/template (a second view class). But it was generated with a protected ctor. Here's the code explanation with comments.
I'm thinking all the normal classes of the Doc/View template are created starting with this code, but within the template code base.
Code:
CSingleDocTemplate* pDocTemplate;
pDocTemplate = new CSingleDocTemplate(IDR_MAINFRAME,
RUNTIME_CLASS(CViewSwitchDoc), //<-expands to-> ((CRuntimeClass*)(&CViewSwitchDoc::classCViewSwitchDoc)),
RUNTIME_CLASS(CMainFrame), // main SDI frame window
RUNTIME_CLASS(CViewSwitchView));
But I have generated "another view" using the "Add Class" Wizard, it's a derived class of mfc CFormView which I named ViewForm. However I'm having a problem creating an instance of it because of the generated protected ctor and pulls a compile error of not being able to access ctor. Below are the header and implementation files of this said ViewForm class. How to create an object of this view ? Did I go about it all the wrong way since it's not in the doc/template group ?
// ViewForm.h file
#pragma once
// ViewForm form view
class ViewForm : public CFormView {
DECLARE_DYNCREATE(ViewForm)
[Code] ....
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Sep 18, 2013
How can a member function in my derived class call the same function from its base class?
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Feb 18, 2015
I am creating a class called time and we've had to do operator overloading for <, > , <=, >=, ==, !=, ++, --, >>, <<, * , +, and -.
Well I have done and error checked them all. The only one I cannot seem to get right is the minus and its because of the error checking. I am having issues with times like this
t1 = 0:0:2:3
t2 = 0:0:1:4
t1 - t2 should equal 0:0:0:59 but it returns 0:0:1:-1.
(days:hours:minutes:seconds)
I need it to check for all cases and I just do not know how. Here is the code I have so far:
time operator- (const time& x, const time& y){
time subtract;
subtract.days = x.days - y.days;
subtract.hrs = x.hrs - y.hrs;
subtract.mins = x.mins - y.mins;
subtract.secs = x.secs - y.secs;
[Code] .....
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Apr 25, 2014
I have the following problem on my C++ Program and I am not sure why it is not working. I am creating a infix to postfix program through an inherited class which I am not sure it is working.
#include <iostream>
#include <stack>
using namespace std;
int in_stack_Priority(char a){
if(a == '*' || a == '/')
return 2;
[Code] .....
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Apr 11, 2014
I'm using Visual C++ 2010 Express on Windows 8. What I want to do at the moment, is to create a class to make WinHttp requests easier. This is the code that I'm basically using to build the class: [URL] ....
This is what I got so far. (Completely untested). Example of how I hope that it will work:
HttpRequest MyRequest;
MyRequest.Initialize("Mozilla/5.0 (Windows NT 6.2; WOW64; rv:28.0) Gecko/20100101 Firefox/28.0","","");
htmlCode = MyRequest.SendRequest("www.cplusplus.com","GET","");
cout << htmlCode << endl;
The code:
#include "stdafx.h"
#include <windows.h>
#include <winhttp.h>
#pragma comment(lib, "winhttp.lib")
class HttpRequest {
[Code] ......
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Jun 24, 2014
I'm trying to create a program that will play scales at certain frequencies, but my arrays are not initializing correctly. I've read up to double check what i'm doing but it doesn't seem to be working. My only guess is my use of a global variable.
const int NotesInScale = 8;
class Scales {
private:
//all Major Scales
int CMajor[NotesInScale];
int GMajor[NotesInScale];
[Code] ....
i'm simply trying to put the frequencies in the scales (the numbers in the array) but I keep getting an error. I feel its a simple fix but i'm not seeing it.
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Feb 15, 2014
This exercise is from C++ primer 5th edition. I have not understood everything about constructors, mainly about how they function.
Work prior to the exercise was creating a class called screen with some specifications. This is the class:
Code:
class screen{
public:
using pos = string::size_type;
screen() = default;
private:
pos height = 0;
pos width = 0;
pos cursor = 0;
string contents;
};
The exercise goes as follows:
Exercise 7.24: Give your Screen class three constructors: a defaultconstructor; a constructor that takes values for height and width and initializes the contents to hold the given number of blanks; and a constructor that takes values for height, width, and a character to use as the contents of the screen.
Giving the screen a default constructor was easy. The next part is probably easy aswell, I just dont understand what they mean when they say "and initalize the contents to hold the given number of blanks" and something in the 3rd part when they say "character to use as the contents of the screen".
Think I have made a breakthrough... Would the constructor for the second part look like this:
screen(pos ht, pos wd) : contents(ht*wd) {}
or something?
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Jun 15, 2013
Well, basically, what I've been doing was creating a class that would implement the concept of Double Linked List, but that would behave like a queue ( the STL implementation is deque, or Double Ended Queue ).
The problem occured when I have been trying to generalize the class using templates. I mean, why use only integers ? Why not double or char or what not ?
Worked perfectly before including all the template stuff..
// Source.cpp <=> Main.cpp
#include <iostream>
#include "DList.h"
using namespace std;
int main(void) {
DList<int> *list;
list = new DList<int>();
[Code] .....
The errors returned by the compiler:
Error1error C2955: 'Node' : use of class template requires template argument listc:usersjumperdesktopc++ otherdouble linked listdouble linked listdlist.h6
Error2error C2955: 'Node' : use of class template requires template argument listc:usersjumperdesktopc++ otherdouble linked listdouble linked listdlist.h6
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Dec 4, 2013
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 &'
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Feb 22, 2014
Create a class to store a value that represents number of hours worked and number of days worked. Must ensure that the two representations are always consistent. I have to create 2 files, I'm pretty sure: a .cpp and a .h
This is what I have so far for my .h file (I know it's NOT functional...yet):
#include <iostream>
using namespace std;
class NumDays {
private:
double hours;
double days;
[Code] ...
I don't know how to start / create this .cpp file to define the variables.
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Aug 6, 2014
I've written this class and struct to create a singly linked list. The data is stored in the binary file which I've opened and read. I'm trying to load said data into a class type array. The errors I'm getting are "incompatible types in assignment of 'StatehoodInfo' to char[3]" Lines 130-134 is what I was working on.
#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <string>
#include <cstring> //For char[] string functions
[Code] .....
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Apr 5, 2014
I'm trying to create a public and static field in a class called ResourceManager. But when trying to access the field even from inside the class it wont work. I'm getting this error message:
Error 1 error LNK2001: unresolved external symbol "public: static int ResourceManager::num" (?num@ResourceManager@@2HA)
Here's my code:
ResourceManager.h
Code:
class ResourceManager {
public:
static int num;
static void loadContent();
[Code] .....
I'm using Visual Studio 2012.
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Jan 27, 2015
I want to create a C library function that i can directly call in my code from any .c file having main program.following are codes...code of library function "foo.c"
Code:
#include "foo.h"
int foo(int x) /* Function definition */ {
return x + 5;
} header file "foo.h"
Code:
#ifndef FOO_H_ /* Include guard */
#define FOO_H_
int foo(int x); /* An example function declaration */
}
[code]....
to use this i have to compile the file in below manner...
Code: gcc -o my_app main.c foo.c
My concern here is that i want to compile the main.c and use function without compiling foo.c with i.e.
Code: gcc -o my_app main.c
any user of this function should only compile his program and should be able to use the function, the foo.c file should remain hidden from him
my system is Linux 2.6.18-308.4.1.el5 #1 SMP Wed Mar 28 01:54:56 EDT 2012 x86_64 x86_64 x86_64 GNU/Linux
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