C++ :: Class Member Functions With Pointer Parameters?
Jan 30, 2013
Here is the assignment: (3pts) Given the following class header file, write the class’ source code for each of the accessor and mutator functions listed. (How the functions have listed their parameters, varying between passing by reference and by value.) Don’t forget to comment your code – it counts!
class Album {
private:
char * artist; // band or singer’s name
char * title; // title of the album
[code]....
The input will be an array. My questions: First, am I on the right track?
When using (char * a) for a function, for example, this is passing the address of a, correct? so then *artist=a; changes what the address of a points to?
also, the functions are bool when I would expect void. Why? for all of the set_" " functions, the parameter is *... but for set_record_label it is *&. That appears to be a mistake to me. Is that right?
what is the difference between *& and * as parameters?
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Aug 19, 2014
In the thread "Making a argument optional to function", it is stated that to set default values for arguments of a function you can simply do so in the function definition, like:
int myfunc(int a, int b, int c=3) {...}
This then automatically puts c to 3 in the function body if a call like myfunc(1,2); is made, if I understood correctly. However, this does not seem to hold for class functions. For example, something like:
class classy {
public:
int class_func(int, int, int); // class function prototype
}
int classy::class_func(int a, int b, int c=3) {...}
fails to compile. What I would like is to be able to call class_func outside of this class (by including it as a header in another macro), optionally specifying c. If c is not specified in the call, it should use a default value.
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Sep 27, 2013
If you are doing some big program, usually, how do you organize the files? Put the class and its member in head file, but where to declare non member functions and where to define them? I don't want to put them all in one cpp file. If not, how to make them visible to the main cpp file?
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Jan 3, 2014
#include "stdafx.h"
#include <iostream>
#include <math.h>
using namespace std;
class Calc {
[Code] ....
when i built it, it showed the following errors:
1>------ Build started: Project: rough, Configuration: Debug Win32 ------
1> rough.cpp
1>e:c programs
ough
ough
ough.cpp(17): error C3872: '0xa0': this character is not allowed in an identifier
1>e:c programs
[Code] ....
Need sorting out the errors!!!
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Feb 28, 2014
Suppose I make a class, something like having the constructor being invoked first makes sense, I don't have a problem with that. But, how could I limit access to functions until certain functions are called? Perhaps this isn't built into the language so you can't. And maybe this problem never comes up. For example if you have a set() and get() functions, if they are both public functions, there doesn't seem to be a way for the compiler at least now if set() never gets called you shouldn't call get(). I just see this as error prone if you need to use libraries, you have to know not to do it from documentation instead of something the compiler can check.
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Mar 30, 2013
how to access the private and protected member functions of the class.....
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Sep 27, 2014
This week we are learning to use templates, and I don't understand how to call my member functions with my template based class. I tried the standard convention of calling member functions, but I keep getting an error saying name following"::" must be a class or namespace name. I'm thinking my problem lies with my typename T, but I am unsure. Line 16 is where I am getting tripped up.
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
template<class T>
T Set
{
public:
[Code]...
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Aug 17, 2013
I am supposed to implement the member functions of class Person.
class Person {
public:
Person();
Person(string pname, int page);
void get_name() const;
void get_age() const;
[Code] ....
The code I wrote is below. Where I am struggling is the program does not allow me to input age. Therefore, I cannot test if my temp for age works. It automatically defaults to 0 because it hasn't taken input. Here is my code:
// Program Title: Person function
// Program Description: The program prompts the user for first and last name and age.
// It then prints the output that was provided by the user.
#include<iostream>
#include<string>
using namespace std;
class Person {
[Code] .....
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Jan 10, 2015
I have the following scenario :
Code:
class test {
public :
int num;
};
int main() {
test t1;
test *ptr = &t1;
int test :: *mem_ptr = &test::num;
}
I need to access mem_ptr (pointer to a class member) through :
a. object (t1)
b. pointer to the object (ptr).
How can i do that ?
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Aug 19, 2014
I have the following problem: I am using NLOpt for optimization. The API provides functions to set the objective. This is done as follows:
double objective(const vector<double> &x, vector<double> &grad, void *data)
{
return x[1]*x[0];
}
int main(){
nlopt::opt opti(nlopt::LD_MMA,2);
opti.set_min_objective(objective,NULL);
vector<double> x(2);
[Code]....
Now I want to make the function objective a member of a class:
class Foo {
public:
double objective(...){..}
};
How can I give this method to opti.optimize? If I make objective static I can use
opti.optimize(Foo::objective,NULL);
but I do not want to have a static member. Is it possible to create an object of type Foo and give it to opti.optimize?
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Jan 6, 2013
I'm currently programming a server which uses multiple threads- I have a class for one map in the game. Each map has a thread for timed events(tile regeneration, NPC regeneration, etc.), and a thread for handling NPCs(movement, combat, etc.). A basic structure of the class looks like this:
class Region {
public:
/* game values are here, they are public so
they can be accessed from outside of the class
inside of packet-handling functions and such */
int value;
void *Function();
[Code] ....
The program crashes when I use a member of the same class the function is located in- in the context I have shown about it would crash on "value++".
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Sep 19, 2014
This project is for an embedded micro controller. In the project i wrote a class that generically services uarts. then i declare 6 objects of that class and hand them configurations for each specific uart.
internally all the objects have a send buffer of data that is still to be sent that gets populated by the object member function.
how can i make an array of function pointers that can point to the same member but of six different objects.
for example (not a working one)
class uart {
private:
struct myData {
unsigned char data[20]
int head
int tail
int count;
[Code] ....
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Mar 6, 2013
Below is a working program. Please note that the vector <int*> pointer is declared as a public member of the class A.
The problem arises when I try to make it a private (instead of public). First, let's look at the File 1 below. It compiles and works fine.
File 1: main.cpp (working fine)
#include <vector>
#include <iostream>
using namespace std;
[Code].....
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Sep 21, 2013
I wrote a fuction in C with the prototype 'void raisePowerOf2(int array[],int pow);'
If someone want to find the value of 2^456 ,just have to invoke this function 456 as the value for pow and int array with 2 elements :1 & -1 as the argument for the array.(There I used -1 to denote the end of the array.)
But it seems that this function doesn't give the exact answer
And I tried this from java also,with the same implementation.It produced the answer precisely .
I tried for hours, but unable to detect reasons why this code blok in C doesn't work properly
This is the code in c
Code:
#include<stdio.h>
void raisePowerOf2(int array[],int pow);
int main(){
int a[2]={1,-1};
raisePowerOf2(a,5);
return 0; }
void raisePowerOf2(int array[],int pow){
[Code]...
This is the code in java....
Code:
public class NewClass4 {
void raisePowerOf2(int array[],int pow){
final int len=array.length;
int store[]=new int[len+1];
int qtnt=0;
for(int i=len-1;i>=0;i--){
store[i+1]=(array[i]*2)%10+qtnt;
qtnt=(array[i]*2)/10;
[Code]...
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Sep 21, 2013
I wrote a fuction in C with the prototype
'void raisePowerOf2(int array[],int pow);'
If someone want to find the value of 2^456 ,just have to invoke this function 456 as the value for pow and int array with 2 elements :1 & -1 as the argument for the array.(There I used -1 to denote the end of the array.)
But it seems that this function doesn't give the exact answer
And I tried this from java also,with the same implementation.It produced the answer precisely .
I tried for hours, but unable to detect reasons why this code blok in C doesn't work properly .
This is the code in c
#include<stdio.h>
void raisePowerOf2(int array[],int pow);
int main(){
int a[2]={1,-1};
raisePowerOf2(a,5);
return 0;
} void raisePowerOf2(int array[],int pow){
[Code] ....
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Mar 11, 2014
we were given this code:
// Music Shuffle Program
// This program takes an array of strings and randomly permutes their order.
// This allows us to generate new song shuffles.
#include <iostream>
[Code]....
or are they referring to something else?
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Jun 22, 2013
I'm trying to write a simple Delegate class with a Bind() and Invoke() function. For now it only needs to support a void class function with no parameters. I've searched around and found quite a few exmaples, though, those class are heavily templated and I lose track trying to simplify it.
So far my code is following:
Code:
#include <windows.h>
class Test {
public:
void DoSomething() {
MessageBox(NULL, L"Test::DoSomething!", NULL, 0);
[Code] ....
The part I am having difficulty with is assigning &Test::DoSomething to the m_Callback variable.
&tObject::DoSomething works, yet _Callback which I pass &Test::DoSomething to does not work.
Also, why does the following line work:
Code:
m_Callback = &Wrapper<tObject, &tObject::DoSomething>;
When wrapper is like:
Code:
template<class tObject, void (tObject::*Func)()>
void Wrapper(void* Object)
Should it not be Wrapper<class-typename, parameter-1>(parameter-2) // This currently creates an error
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Aug 6, 2013
void func(float arg); // arg is supposed to be in type, with no referencing, just a copy of it
void func(float &arg); // arg is supposed to be in, out type, with something contained in it already
void func(float *arg); // arg is supposed to be in-out type, with nothing contained in it already and can be NULL
void func(const float& arg) // arg is supposed to be in type, with nothing contained in it already and cannot be NULL
Am I all correct?
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Mar 27, 2013
Summary: 6 companies have a product in 5 different warehouses. Each company is identified by a positive ID number and each warehouse is identified by a number (1 for the first, 2 for the second,…)
Object: the object of this assignment is to write a C++ program which asks the user to enter a company ID number, and the number of products in each of the warehouses. It then computes and prints the total number of products for that company
If the total number of product is less than 100, it prints the message “place a new order”
Input: for each company, its ID, and the number of products in each warehouse with appropriate prompt messages.
Example: Enter company ID number: 101
Enter number of products in warehouse #1:30
Enter number of products in warehouse #2:60
Enter number of products in warehouse #3:0
Enter number of products in warehouse #4:5
Enter number of products in warehouse #5:27
The total for company 101 is:122
Output: for each company, the total number of product, and the message “place a new order” if the total number of product is less than 100.
Method:
1. Define global variable, int total_prod to hold the total number of products for a company
2. define the function void compute_total() that uses a loop to read the number of the products in all warehouses for one company, computer the total number of products and store it into the global variable total_prod.
3. Define the function void new_order() that determines if a new order need to be placed as follows: if the total number of products (in the global variable total_prod) is less than 100, it prints the message “place a new order”
4. Your function main does the following in a loop:
- read a company ID number
- call function compute_total() to read the number of the product in all warehouses for that company, and to compute their sum
- print the total number of the product for that company with an appropriate message
- call the function new_order() to determine if a new order need to be placed.
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Mar 16, 2013
What would be the correct way to call a function within main that has file pointer parameters?
function prototype: Code: void CalculateBoth(int num1, int num2, int*sumPtr, int *diffPtr);
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Feb 6, 2015
I create an instance of a base class (not derived class) and assign it to base class pointer. Then, I convert it to a pointer to a derived class and call methods on it.
why does it work, if there is a virtual table?
when will it fail?
// TestCastWin.cpp : Defines the entry point for the console application.//
#include "stdafx.h"
#include <iostream>
class B
{
public:
B(double x, double y) : x_(x), y_(y) {}
double x() const { return x_; }
[Code] ....
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Mar 20, 2014
I'm a little confused by my programming assignment this week. I've been working at it Wednesday and I've made progress but I'm still confused as to how I'm supposed to do this. The class I made is called Stack, and it's derived from a template class called StackADT. We also utilize a class called unorderedLinkedList, which is derived from a class called linkedList.
We're supposed to implement all of the virtual functions from stackADT in the Stack class. The Stack data is stored in a an unorderedLinkedList, so what I'm confused by is how to implement a few of the Stack functions because there are no functions in unorderedLinkedList which we could call to manipulate the data.
As you can see from my attached code, I'm really confused by how I'm supposed to implement the pop() and top() functions, and I also think my initializeList() function is wrong. We don't have any similar functions in unorderedLinkedList to call, so I'm at a loss of how i'd access my unorderedLinkedList. My initial thought was to call the similar functions in the class that unorderedLinkedList was derived from, linkedList, but I'm unsure of this is what we're supposed to do, or if theres actually a way to access my unorderedLinkedList without having to use the functions from the base class.
NOTE: We're not allowed to modify stackADT, unorderedLinkedList, and linkedList.
Stack.h
#include "stackADT.h"
#include "unorderedLinkedList.h"
template<class Type>
class Stack: public stackADT<Type>{
template <class T>
struct nodeType
{
T info;
nodeType<T> *link;
[Code]...
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Aug 31, 2014
So I have a class object that contains the private member variable spot and the public member function MoveLock. Within MoveLock, is a member variable called numbers that holds the place where a user is on a "lock knob". Now, what I'm trying to accomplish is that whenever the user turns the "knob" in the wrong direction, the position is updated with that current numbers so that the clicks needed to unlock the first state is also updated. But I get these errors:
Error E2096 C:Users...switchtest.cpp 34: Illegal structure operation in function main()
Error E2294 C:Users...switchtest.cpp 39: Structure required on left side of . or .* in function main()
Ultimately, what I have in main() is a piece of what I'm going to implement in a class member function. I'm also thinking about moving the if else statements out of the for and creating a second one for the else portion.
#include <iostream>
#include <windows.h>
#include <iomanip>
using namespace std;
HANDLE inKeys = GetStdHandle(STD_INPUT_HANDLE);
HANDLE screen = GetStdHandle(STD_OUTPUT_HANDLE);
[code]....
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May 3, 2013
At the moment im trying out with pointing to an array of functions. I got this working as following:
typedef void (* functionPtr) ();
functionPtr functions[2][2]={{do11,do12}, {do21,do22}};
void do11(){DEBUG_PRINTLN("11");}
void do12(){DEBUG_PRINTLN("12");}
void do21(){DEBUG_PRINTLN("21");}
void do22(){DEBUG_PRINTLN("22");}
void loop(){
A=0;
B=1;
functions[A][b]();
}
But now I'm trying to use this to point to a function inside a class so instead of do11, i want to be able to point to Basic.Do11. Somehow this doesnt work and I keep on getting this message:
error: argument of type 'void (Basic::)()' does not match 'void (*)()'
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Mar 5, 2014
Assume a class named Dollars exists. Write the headers for member functions that overload the prefix and postfix ++ operators for that class.
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Jan 24, 2013
Code:
class Editor {
// c'tors etc
Gtk::EventBox canvas_event_box;
void functionA();
void functionB() const;
[Code] ....
When I try to compile functionB in Visual C++ it gives me this error:-
glibmm/refptr.h(199) : error C2440: 'initializing' : cannot convert from 'const Gdk::Window *' to 'Gdk::Window *'
Conversion loses qualifiers
And this is the code from glibmm/refptr.h
Code:
// The templated ctor allows copy construction from any object that's castable. Thus, it does downcasts:
// base_ref = derived_ref
template <class T_CppObject>
template <class T_CastFrom>
[Code] .....
I don't actually want to change anything in the member variable canvas_event_box. I just want to be able to call one of its functions from my 'const' member function. Is there any syntax I can use to tell VC++ that I'm not actually changing the variable - just using it.
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