copying an array into another

[G1vDizwU]

Hi guys,

Consider we have an array like this:

int ar1[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

We want to initialize a second one, ar2, as a copy of ar1:

int ar2[10];

How many ways are there for doing it please?

[LA48b7Xj]

Here are 3 ways to do it

#include <algorithm>
#include <iostream>

using namespace std;

void f1()
{
    int ar1[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int ar2[10];

    copy(begin(ar1), end(ar1), begin(ar2));

    for(auto e : ar2)
        cout << e << ' ';
    cout << '\n';
}

void f2()
{
    int ar1[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int ar2[10];

    for(int i=0; i<10; ++i)
        ar2[i] = ar1[i];

    for(auto e : ar2)
        cout << e << ' ';
    cout << '\n';
}

void f3()
{
    int ar1[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int ar2[10];

    int* p = ar1;
    int* q = ar2;

    while(p != ar1 + 10)
        *q++ = *p++;

    for(auto e : ar2)
        cout << e << ' ';
    cout << '\n';
}

int main()
{
    f1();
    f2();
    f3();
}

[G1vDizwU]

Thank you for your reply.

[mbozzi]

It's maybe worth mentioning that
ar2 = ar1
Doesn't copy the array.

[G1vDizwU]

Thanks mbozzi. Good point, yeah. :)

[iN6fizwU]

mbozzi is correct that
ar2 = ar1
doesn't copy elements if ar1 and ar2 are int arrays.

Being slightly pedantic, perhaps, it would copy array elements if ar1 and ar2 were declared as
valarray <int>
which, incidentally, makes valarrays behave like standard Fortran 90/95 arrays. Heresy to talk about Fortran on a C++ forum, I guess.