使用模板…我的代码有什么问题？

Question

I just recently was learning templates in C++. But I got 3 errors even when I do everything exactly like in my course.

This is the main.cpp:

#include <iostream>
#include "szablony.h"

using namespace std;

int main()
{
    cout << nmax<int>(55,402) << endl;

    Klasa<double> a1;
    a1.ustaw(25.54);

    Klasa<double> a2;
    a2.ustaw(44.55);

    cout << a1.podaj() << " :max: " << a2.podaj() << " = " <<
    nmax<Klasa>(a1.podaj(),a2.podaj()) << endl;

}

And this is "szablony.h":

#include <iostream>

using namespace std;

template <typename T> class Klasa
{
    T wartosc;

public:

    template <typename U> T podaj()
    {
        return (this -> wartosc);
    }

    template <typename U> void ustaw(U war)
    {
        wartosc=war;
    }
};

template <typename T, typename T1, typename T2> T nmax(T1 n1, T2 n2)
{
    return (n1 > n2 ? n1 : n2);
}

template <> Klasa nmax<Klasa>(Klasa n1, Klasa n2)
{
    return (n1.podaj() > n2.podaj() ? n1 : n2);
}

So these are the errors:

1. "szablony.h":|line 27|error: invalid use of template-name 'Klasa' without an argument list|

2. main.cpp|line 16|error: no matching function for call to 'Klasa::podaj()'|

3. main.cpp|line 17|error: no matching function for call to 'Klasa::podaj()'|

This course is from 2004 btw, that's probably one reason, but even when I look on the internet, everything seems ok...

Thank you in advance :)

Answer 1

The main problem is that Klasa is a template class, but you use it in the specialization of nmax as a regular class. In particular, Klasa does not represent a type, but eg Klasa<int> does.

So either make your function return a template template, or use Klasa<type>