isclasst.cpp

C++ Templates 完全导引范例

/* The following code example is taken from the book
 * "C++ Templates - The Complete Guide"
 * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
 *
 * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include "isclasst.hpp"

class MyClass {
};

struct MyStruct {
};

union MyUnion {
};

void myfunc()
{
}

enum E { e1 } e;

// check by passing type as template argument
template <typename T>
void check()
{
    if (IsClassT<T>::Yes) {
        std::cout << " IsClassT " << std::endl;
    }
    else {
        std::cout << " !IsClassT " << std::endl;
    }
}

// check by passing type as function call argument
template <typename T>
void checkT (T)
{
    check<T>();
}

int main()
{
    std::cout << "int:     ";
    check<int>();

    std::cout << "MyClass: ";
    check<MyClass>();

    std::cout << "MyStruct:";
    MyStruct s;
    checkT(s);

    std::cout << "MyUnion: ";
    check<MyUnion>();

    std::cout << "enum:    ";
    checkT(e);

    std::cout << "myfunc():";
    checkT(myfunc);
}