A pointer Problem

[systempause]

Hi i wrote some code to calculate the max value of an array or something like this but i couldnt find the error in the program but i think the pointer created in main function doesnt send the address to the fuction .Could you help me with this?
CODE IS HERE

#include <iostream>
using namespace std;

double max(double *x[],int n){
       double *maks;
       maks = *(&x[0]);
       cout << "maks " << maks << endl;
       cout << *(&x[2]) << endl;
       cout << *maks << endl;
       for(int i=0;i<n;i++) {
               if(*maks < **(&x[i])) maks = *(&x[i]);
               
               }
       return *maks;
       }

int main(){
    int n=3;
    double *ptr;
    
    ptr = new double[n];
    
    for(int i=0;i<n;i++) cin >> *(ptr+i);
    cout << *(ptr+1) << endl;
    double v;
    v = max(&ptr,n);
    cout << "max = " << v << endl;
    
    delete [](ptr);
    
    
    system("pause");
    return 0;
    }
 

[Athar]

You really should have a look at the pointer chapter again.

Fixed version:

#include <iostream>
using namespace std;

double max(double* x,int n)
{
  double maxVal=x[0];
  for(int i=1;i<n;i++)if (x[i]>maxVal)maxVal=x[i];
  return maxVal;
}

int main()
{
  const int n=3;
  double vals[n];
  for (int i=0;i<n;i++)cin >> vals[i];
  cout << "max = " << max(vals,n) << endl;
}

[systempause]

Thank you for your advice but i can write code like this you wrote.However i am expected to write a program including a function which is in the form like double max(double *x[],int n).I wonder whether a function doing the same work can be wroten in thsi type.Thanks for your help...

[systempause]

Is there anyone who can help me with it??

[systempause]

Is there anyone there???Please help me with thsi...

[Galik]

For your parameter, double *x[], you can do:

double d = *(x[0]); // because x[0] is a pointer to a double

// So to visit every double you would need to dereference every double pointer in the array:

for(int i = 0; i < n; ++i)
{
    if(*(x[i]) > max) { max = *(x[i]); }
}

So all you need to do is figure how to create such an array.

Remember you need an array of double pointers. Pointers to type double:

double* x[size];

So you need to allocate memory to every pointer in the array in which to store your doubles:

x[0] = new double; // allocate a double to element 0 of the double pointer array. 

And you need to delete all those pointers afterwards:

delete x[0]; // delete element 0 of the double pointer array 

[systempause]

Thanks for your support but this isnt the answer of my question because i must use a function like
double max(double *x[],int n){ } .anyway.And Could you write your own code in the way of solution you describe??

[Galik]

I have explained how to use the kind of array you are expected to use but I am not going to do your assignement for you.

You have to learn these concepts for yourself.

So you try to write your code using the information I provided and I wall do my best to explain if you make a mistake.

[Galik]

I think your code for double max(double *x[],int n){ } works fine.

There is a problem in the way you create your array to sent to that function:

    double *ptr; // pointer to array of type double
    
    ptr = new double[n]; // array of type double 

That creates an array of type double. But the function max() expects an array of type double*

[systempause]

I edited the code there is still a mistake...

#include <iostream>
using namespace std;

double max(double *x[],int n){
   double max = *(x[0]); 
   for(int i = 0; i < n; ++i) 
   {
    if(*(x[i]) > max) { max = *(x[i]); }
    }
    return max;
    }

int main(){
    int n=3;
    double *ptr; 
    
    ptr = new double[n]; 
    cout << max(ptr,n) << endl;
    
    cin.ignore(2);
    return 0;
    }
 

[systempause]

Thsi is what i am trying to tell you...

[Galik]

The problem is that your function is like this: double max(double *x[],int n){ } :

So you need to be creating one of these:

double* x[]; // Array of double pointers OR array of double*  

BUT you are creating one of these:

double ptr[]; // Array of double 

Because that is conceptually the same as:

double* ptr; // Array of double 

So you need one of these:

double* ptr[]; // Array of double* 

Or one of these:

double** ptr; // Array of double* 

[Galik]

I recommend you do this:

double* ptr[n]; // Array of n double pointers 

And for each one allocate a double using new a bit like this:

double* ptr[0] = new double; // allocate a new double for the first pointer in the array 

[systempause]

Thanks this solved my problem exactly...By the way it is not a homework assignment.

[Galik]

systempause wrote:

By the way it is not a homework assignment.

Heh, so you're just torturing yourself for the fun of it? ;o)

[systempause]

Yep.There are several methods to write a program doing the same task but i want to explore new ones