problem operator

**llynx** · 10-19-2009

i have one problem, function sort and dynamic array , program dont run, error, can you help me, find error and fix it.

thanks very much.

Code:

class MyIntArray{
public:
	MyIntArray(int N); 
	~MyIntArray();
	int operator [](int i);
	MyIntArray &operator=(const MyIntArray &A);
	void sort();
private:
	int *ptr;
	int len;

};

Code:

#include"MyIntArray.h"
#include"iostream"
#include "string"
int N =10;
//using namespace std;
MyIntArray::MyIntArray(int N){ // allocate array of N integers
	ptr=new int[N];
}
MyIntArray::~MyIntArray(){
	delete ptr;
}
int MyIntArray::operator [](int i){ 
	return ptr[i];
}

MyIntArray &MyIntArray::operator =(const MyIntArray &A){
//	len=(int)strlen(ptr.);
	//A=new int[N];
	for(int i=0;i<N;i++){
		A[i]=ptr[i];
	}
	return (*this);
}

void MyIntArray:Sort(){ 
	int tmp;
	for(i=0;i<len;i++){
		for(int j=i;j<N;j++){
			if(ptr[j]>ptr[j+1]){
				tmp=ptr[j];
				ptr[j]=ptr[j+1];
				ptr[j+1]=tmp;
			}
		}
	
	}
}

Code:

MyIntArray IArr(5); // allocate array of 5 integers
for (int i=0; i<5 i++)
	cin >> IArr[i]; // input value from user
cout << “before sorting:” << endl;
cout << IArr << endl;
MyIntArray IAS(1);
IAS = IArr;
IAS.Sort();
cout << “after sorting:” << endl;
cout << IAS << endl;

**Sebastiani** · 10-19-2009

>> ptr=new int[N];

You need to set 'len' to 'N', and stop using the global 'N' inside the class.

>> delete ptr;

For arrays, you need delete [].

>> len=(int)strlen(ptr.);

Come on, now, strlen? That's for null-terminated char arrays. Just use the 'len' member of 'A' to get the new size (don't forget to delete the old data, either).

>> void MyIntArray:Sort()

Bubble sort.

>> ~MyIntArray();

Just for good measure, make this virtual, in case someone tries to derive from MyIntArray (to ensure that the destructor gets called).

Also, you need to either define the copy constructor (internally, it can simply call operator =, but just be sure to initialize your pointer to 0 first), otherwise, make it private.

**laserlight** · 10-19-2009

Originally Posted by Sebastiani

Just for good measure, make this virtual, in case someone tries to derive from MyIntArray (to ensure that the destructor gets called).

I do not agree: the class has no virtual functions otherwise, and there is nothing that suggests that it was intended to be a base class.

Speaking of implementing the copy constructor: you may find that it is easier to implement the copy constructor, and then implement the copy assignment operator using the copy constructor, with the help of a swap function that just swaps the length and pointer to int (you also get hidden help from your destructor).

**llynx** · 10-19-2009

thaks Sebastiani

Code:

Just use the 'len' member of 'A' to get the new size (don't forget to delete the old data, either).?

i still vague.
Sebastiani , can talk detail it ? or give example. thanks

**laserlight** · 10-19-2009

Sebastiani's point is that the object that you are copying from already knows the size of its array segment that is in use. If you were storing a null terminated string instead, then you could indeed use strlen(), but it would still be unnecessary since the size is already known.

**llynx** · 10-19-2009

you can fix it help u? thanks

Code:

Sebastiani's point is that the object that you are copying from already knows the size of its array segment that is in use. If you were storing a null terminated string instead, then you could indeed use strlen(), but it would still be unnecessary since the size is already known.

i simple want understand it if it run true.
thanks laserlight

**laserlight** · 10-19-2009

Originally Posted by llynx

i simple want understand it if it run true.

It is just a matter of:

Code:

len = A.len;

Notice that I am assigning A.len to len, not len to A.len. You have a similiar problem when you try to copy the elements of the array over. But you completely forgot to destroy the old array's elements. To do this correctly, you need a temporary pointer to hold the new array... but frankly, I suggest that you just implement the copy constructor and a member swap function first, then we'll show you how to implement the copy assignment operator.

**llynx** · 10-19-2009

thanks laserlight , but i think, i have one swap is true.?

**llynx** · 10-19-2009

i have constructor, how do you understand about it?

Code:

MyIntArray::MyIntArray(int N){ // allocate array of N integers
	len=N;
	ptr=new int[len];
}

but when i run it, the output address, after sort();

**Sebastiani** · 10-19-2009

Originally Posted by llynx

thanks laserlight , but i think, i have one swap is true.?

Your statement doesn't make much sense. If English is not your native language, that's fine, but just be sure to use as many words as necessary to communicate the general idea clearly.

**Sebastiani** · 10-19-2009

Originally Posted by llynx

i have constructor, how do you understand about it?

Code:

MyIntArray::MyIntArray(int N){ // allocate array of N integers
    len=N;
    ptr=new int[len];
}

but when i run it, the output address, after sort();

Your constructor looks fine. I'm not sure what you mean in the following sentence, though.

**llynx** · 10-19-2009

thanks Sebastiani, after i fix it, but the output is address after sort();
you can help me ? thanks very much.

Code:

#include"MyIntArray.h"
#include"iostream"
#include "string"
int N=10;
//using namespace std;
MyIntArray::MyIntArray(int N){ // allocate array of N integers
	len=N;
	ptr=new int[len];
}
MyIntArray::~MyIntArray(){
	delete []ptr;
}
int &MyIntArray::operator [](int i){ 
	return ptr[i];
}

MyIntArray &MyIntArray::operator =(const MyIntArray &A){
	//A.len=;
	len=A.len;
	ptr=new int[A.len];
	for(int i=0;i<len;i++){
		A.ptr[i]=ptr[i];
	}
	return (*this);
}

void swap(int *x, int *y)
{
     int temp;
     temp = *x;
     *x = *y;
     *y = temp;
}

int compare(int x, int y)
{
     return(x > y);
}

void MyIntArray::Sort(){ 
for(int i = 0; i <=len; i++)
     {
          for(int j = 0;j< len; j++)
          {
               if(compare(ptr[j], ptr[j+1]))
                  swap(&ptr[j], &ptr[j+1]);
          }
   }
}

**llynx** · 10-19-2009

this is void main()

Code:

#include"MyIntArray.h"
#include"iostream"
using namespace std;
void main(){
	
MyIntArray IArr(5); // allocate array of 5 integers
for (int i=0; i<5 ;i++)
	cin >> IArr[i]; // input value from user
	cout << "before sorting:" << endl;
	//cout << IArr << endl;
	for(int i=0;i<5;i++){
		cout<<IArr[i]<<" ";
	}
	MyIntArray IAS(5);
	IAS = IArr;
	IAS.Sort();
	cout << "after sorting:" << endl;
	for(int i=0;i<5;i++){
		cout<<IAS[i]<<" ";
	}
	//for(int i=0)
}

http://upanh.com/uploads/19-Sep-2009...ayq8y6css8.png

**llynx** · 10-19-2009

why dont you help me?

**llynx** · 10-19-2009

thanks Sebastiani &laserlight very much

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