Another template question...

Hi (again) :)

I just want to check that this is the correct way to use templates. I have just done an exercise from my book that requires me to create a template class that holds pairs of data. So I chose string name and int age. Then to store them in a vector to be able to access.

My code is:

Code:

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template <class T, class U> class pairs
{
public:
        pairs(T n, U a)
                :name(n), age(a) {}



        T name;
        U age;
};

int main()
{
 
        vector<pairs<string, int>> pair;

        string name;
        int age;

        while(cin >> name >> age)
                        pair.push_back(pairs<string, int>(name, age));


       
        for(int i = 0; i < pair.size(); ++i) {
                cout << pair[i].name << '\n' << pair[i].age << endl;
        }

       
        cin.get();

        return 0;
}

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The code works, and I am aware that the data members of the class should be private. I've just left them public for ease of access.

Is this the correct way to implement templates and to use them to store information in a vector?

Thanks.

Looks good. I know this was done as an exercise, but you might also read up on std::pair to see what the standard library does differently.

Okay thanks. I wasn't aware of std::pair. WIll have a read up on it.

Just two notes:

• It's possible to write typename instead of class. The class keyword is actually an old keyword maintained for backwards compatibility.
• Be careful with T1<T2<T3>>. This is not valid C++03 (two > in template declarations must not exist in C++03; separate them with spaces), but it is valid C++0x.

Quote:

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Originally Posted by Elysia

Just two notes:

• It's possible to write typename instead of class. The class keyword is actually an old keyword maintained for backwards compatibility.
• Be careful with T1<T2<T3>>. This is not valid C++03 (two > in template declarations must not exist in C++03; separate them with spaces), but it is valid C++0x.

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First point is noted. Will use typename from now.

I'm not sure how you mean with the 2nd point. How should the template declaration have been written for C++03?

Thanks again.

Quote:

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Originally Posted by darren78

I'm not sure how you mean with the 2nd point. How should the template declaration have been written for C++03?

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I forgot about this since my compiler has extensions allowing it. The problem is a potential parse error caused by '>>'.

Code:

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vector<pairs<string, int>> pair;

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C++03 will interpret >> as operator>>, not as the closing brackets of a template. To fix it, you have to include spaces.

Code:

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vector<pairs<string, int> > pair;

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Okay, thanks for that.