Array contents equality in C++

Is there a way to get the equality operators to work for comparing arrays of the same type?

For example:

int x[4] = {1,2,3,4};
int y[4] = {1,2,3,4};
int z[4] = {1,2,3,5};
if (x == y) cout << "It worked!"

I'm aware that as is, it's just comparing pointer values - but I was hoping there's some kind of typedef trick or something like that so it wouldn't need a loop or a mem开发者_Python百科cmp call.

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You can use standard equal algorithm

if (std::equal(x,x+4,y)) cout << "It worked!";

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Use std::equal as:

if(std::equal(x, x+ xsize, y)) std::cout << "equal";

It checks equality of elements in the same order. That means, according to std::equal the following arrays are not equal.

int x[4] = {1,2,3,4};
int y[4] = {1,2,4,3}; //order changed!

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Another way would be to wrap your arrays in the std::array template, which will make a small wrapper class for the array. Everything works pretty much like normal, except that you get a default definition of operator=, so you can use == as normal to do the expected thing.

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Since the arrays are of the same type and length, you could use memcmp to test for equality, that is equality of value and position:

int array1[4] = {1, 2, 3, 4};
int array2[4] = {5, 6, 7, 8};

if (memcmp(array1, array2, sizeof(array1)) == 0)
{
    cout << "arrays are equal" << "\n";
}
else
{
    cout << "arrays are not equal" << "\n";
}

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I think its also useful to note here that C++ does not allow you to overload operator== without at least 1 user-defined type. That would be the "nice" solution, but even if you could, it would probably be a bad idea. Arrays in C++...are sort of evil woodland creatures.

std::equal is probably your best bet. Though you could probably do what you want with a *gasp* macro, i think that is gacky.