CODEWITHSUNDEEP
c++arraysvector
user12971631
user12971631

Reputation:

C++ error when instantiating a vector of int arrays (vector<array<int, 3>>)

I am new to C++, so this is probably just a simple mistake, but when I try to create a vector of integer arrays, for example vector <array<int, 3>> triangles = ({0, 1, 2}, {3, 4, 12});, I get this error:

error: expected ';' before '}' token
       vector <array<int, 3>> triangles = ({0, 1, 2}, {3, 4, 12});
                                                   ^

I am using the CMake version included with CLion 2020.1.1 for compilation. The full script is below:

#include <iostream>
#include <vector>
#include <array>
using namespace std;

int main() {

    vector<array<int, 3>> triangles = ({1,2,3},{2,3,4});
    cout << triangles;

    return 0;
};

Thank you, any help is greatly appreciated :)

Upvotes: 0

Views: 207

Answers (3)

Farhad Sarvari
Farhad Sarvari

Reputation: 1081

 #include <iostream>
 #include <vector>
 #include <array>
 #include <algorithm>
 using namespace std;

 int main() {

     vector<array<int, 3>> triangles = {{1,2,3},{2,3,4}};
     
     for_each (triangles.begin(), triangles.end(), [](array<int,3> arr) {for (int item2 :arr) {cout << "[" << item2 << "]"<< endl; ;}});

     return 0;
 };

Upvotes: 0

StPiere
StPiere

Reputation: 4253

Instead of brackets ({1,2,3},{2,3,4}) you should be using curly braces for initializer list: {{1,2,3},{2,3,4}};

Also there is no default operator<< for vector - you have to define your own.

#include <iostream>
#include <vector>
#include <array>
using namespace std;

int main() {

    vector<array<int, 3>> triangles = {{1,2,3},{2,3,4}};
    //cout << triangles;  // there is no default operator<< for vector - you have to define one on yourself

    return 0;
}

for example:

#include <iostream>
#include <vector>
#include <array>
using namespace std;

using MyContainer = vector<array<int,3>>;  // using type-alias for making life easier

ostream& operator<<(ostream& os, const MyContainer& v)
{
    for (const auto& arr : v)
    {
        for (const auto& el : arr)
            os << el << " ";
        os << "\n";
    }
    
    return os;
}

int main() {
    
    MyContainer triangles {{1,2,3},{2,3,4}};
    //cout << triangles;  // there is no default operator<< for vector - you have to define one on yourself
    cout << triangles;

    return 0;
}

Output:

1 2 3 
2 3 4

Upvotes: 1

Waqar
Waqar

Reputation: 9366

Your syntax is incorrect, hence the error.

Try the following:

int main() {

    vector<array<int, 3>> triangles {{1,2,3},{2,3,4}};
    //cout << triangles;
    for (const auto& triangle : triangles)
        for (const auto i : triangle)
            cout << i << '\n';

    return 0;
};

Moreover, you can not directly output a vector. You have to iterate over its elements and print them out one by one.

vector<array<int, 3>> triangles {{1,2,3},{2,3,4}}; syntax is known as "direct-list initialization", while vector<array<int, 3>> triangles = {{1,2,3},{2,3,4}}; is "copy-list initialization". Read more about them here: Differences between direct-list-initialization and copy-list-initialization

Upvotes: 0

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