Thread: function to copy an array->something going wrong with sizeof()

You can only get the correct sizeof result if you pass the array by reference.

Code:

void printArray(int (&a)[4])
{
    cout << "sizeof(testArray) in f-call: " << sizeof(a) << endl;
    int lengte = sizeof(a) / sizeof(int);
    cout << lengte;
    for (int i = 0; i < lengte; ++i)
        cout << a[i] << " ";
    cout << endl;
}

Of course, this makes using sizeof rather pointless, because this function can only accept arrays of 4 integers and nothing else.

You could make that into a template:

Code:

template <std::size_t N>
void printArray(int (&a)[N])
{
    cout << "sizeof(testArray) in f-call: " << sizeof(a) << endl;
    int lengte = sizeof(a) / sizeof(int);
    cout << lengte << '\n';
    for (int i = 0; i < lengte; ++i)
        cout << a[i] << " ";
    cout << endl;
}

which would still make sizeof pointless, because now you'd already know how many items there are.

Or you could use a real array class (to be added to the C++ standard library).

Code:

#include <iostream>
#include <boost/array.hpp>
using namespace std;

template <class Container>
void printArray(const Container& c)
{
    for (int i = 0; i < c.size(); ++i)
        cout << c[i] << " ";
    cout << endl;
}

int main(int argc, char *argv[])
{
    boost::array<int, 4> testArray = {2, 1, 2, 3};
    printArray(testArray);
    //mergeSort(testArray);
    return 0;
}

std::array is available in C++0x, though. Just use the newest version of Visual Studio Express or GCC.

Originally Posted by Elysia

std::array is available in C++0x, though.

boxden, in case you did not know, C++0x is a name for the next version of the C++ standard, so Elysia is merely confirming what anon mentioned that this "real array class" (template) is "to be added to the C++ standard library". As of now, you may be able to use std::tr1::array, which should be the same as the would-be std::array.