Thread: array passing

What i'm wondering is if there is an easy way to pass a copy of an array to a function. in the following program i pass the address of an array of numbers, a, to the change function. But what i really want to do is pass a copy so that the function change can not change a. How can i do this?

Code:

#include <iostream>

void swap (int &a, int &b) {
int temp;
temp=a;
a=b;
b=temp;
}

void display (int numbers[5]) {
for (int i=0; i <5; i++)
std:: cout << numbers[i] << ",";
std::cout << "\n";

}     
void change (int numbers[5]) {
  numbers[0]=100;numbers[1]=100;numbers[2]=100;
  display(numbers);

}


int main(void) {
int a[]={1,5,6,8,3};
std::cout << "before organize and print a="; display(a);
change(a);
std::cout << "after a="; display(a);
system("PAUSE");
return 0;
}

Well maybe you can add a const to your function head so that it won't change ur parameters
else try to copy the whole array to either another array or maybe even a dynamic array so u can delete the array later..
Use:
something like this:

typeOfYourPointer *ptrName;

ptrName = new YourArrayType [];

to create a dynamic array
and delete it later like this

delete prtName;

hope i help a bit ;P

Originally posted by manwhoonlyeats
What i'm wondering is if there is an easy way to pass a copy of an array to a function. in the following program i pass the address of an array of numbers, a, to the change function. But what i really want to do is pass a copy so that the function change can not change a. How can i do this?

The easiest way is to encapsulate your array int a container and have your function take the container by value (and you can template the function to make it use that definition for all container types). I'd suggest using boost::array< int, 5 > (boost.org) if you are sure that you always need an array of 5 elements, or you can use std::vector (but I wouldn't recommend it as it forces dynamic memory allocation unless you wanna have some fun with allocators).
Another quick solution would be to encapsulate your array in a struct and let the default copy constructor do the work (but I don't recommend it).
Finally, you could always just manually copy all of the elements from within the functions, but I don't recommend that at all.

Also, just as a side note, your current functions are set up to accept pointers to ints. If you want the functions to only take arrays of ints of length 5 (passed by reference), then use

void change( const int (&numbers)[5] ) // a reference to an array of 5 const ints