Class template + function call = error

[Larry2]

Hi,

I am trying to become familiar with templates.

My goal : cout char if the object is initialized with a char, number otherwise.

Just a training.

Unfortunately, I might have missed something :)

#include <iostream>

using namespace std;

template <class T>
class Bilou {
    private :
    T a;

    public :
    Bilou(T a){};
    T tiger();

};
template <>
class Bilou <char> {
    private :
    char a;

    public :
    Bilou(char a){};
    char tiger2();

};

char tiger2 () {

cout << "char";}

template <class T>
T Bilou<T>::tiger(){
cout << "number";}

int main(int argc, char *argv[])
{

    Bilou <double>obj(54);
    obj.tiger(); //here is the faulty line
    return 0;
}

and the compiler shout after me :
required from here

where the line calls the function tiger (commented the code accordingly).

How can I manage it ?
Is it theoretically possible ?

Even with <double>obj.tiger(), it breaks.

Any suggestion ?

Thanks !

Larry

[Peter87]

You have forgot to return a value from tiger().

[Larry2]

Indeed Peter, that was that !

    Bilou <double>obj(54);
    double c = obj.tiger(); //here is the faulty line
    if (c)
    cout << "num";

Many thanks !

Cheers,

Larry

[Larry2]

A better coding : with same class but specialized functions :

#include <iostream>
#include <string>
using namespace std;

template <class T>
class Bilou {
    private :
    T a;

    public :
    Bilou(T a){};
    int tiger();

};


template <>
int Bilou<char>::tiger() {

return 1;}

template <class T>
int Bilou<T>::tiger(){
return 2;}

int main(int argc, char *argv[])
{

    Bilou <double>obj(54);
    Bilou <int>obj2(54);
    Bilou <char>obj3('q');
    int c = obj2.tiger();
    int q = obj3.tiger();

    cout << c << endl << q << endl;


    return 0;
}

[JLBorges]

#include <iostream>

struct Bilou
{
    static char Tiger( char ) { std::cout << "char: " ; return 'A' ; }

    template < typename T >
    static int Tiger( T ) { std::cout << "not char: " ; return 9 ; }
};

int main()
{
    std::cout << Bilou::Tiger('A') << '\n' ; // char: A
    std::cout << Bilou::Tiger(23) << '\n' ; // not char: 9
}

[Larry2]

Exact !

My code above was intended to be a starting point for different functions implementations depending on the type.

But I am just a beginner :)