types.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 "typet.hpp"
#include <iostream>

class MyClass {
};

void myfunc()
{
}

enum E { e1 };

// check by passing type as template argument
template <typename T>
void check()
{
    if (TypeT<T>::IsFundaT) {
        std::cout << " IsFundaT ";
    }
    if (TypeT<T>::IsPtrT) {
        std::cout << " IsPtrT ";
    }
    if (TypeT<T>::IsRefT) {
        std::cout << " IsRefT ";
    }
    if (TypeT<T>::IsArrayT) {
        std::cout << " IsArrayT ";
    }
    if (TypeT<T>::IsFuncT) {
        std::cout << " IsFuncT ";
    }
    if (TypeT<T>::IsPtrMemT) {
        std::cout << " IsPtrMemT ";
    }
    if (TypeT<T>::IsEnumT) {
        std::cout << " IsEnumT ";
    }
    if (TypeT<T>::IsClassT) {
        std::cout << " IsClassT ";
    }
    std::cout << std::endl;
}

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

    // for pointer types check type of what they refer to
    if (TypeT<T>::IsPtrT || TypeT<T>::IsPtrMemT) {
        check<typename CompoundT<T>::BaseT>();
    }
}

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

    std::cout << "int&:" << std::endl;
    check<int&>();

    std::cout << "char[42]:" << std::endl;
    check<char[42]>();

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

    std::cout << "ptr to enum:" << std::endl;
    E* ptr = 0;
    checkT(ptr);

    std::cout << "42:" << std::endl;
    checkT(42);

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

    std::cout << "memptr to array:" << std::endl;
    char (MyClass::* memptr) [] = 0;
    checkT(memptr);
}