c++语言编写程序，设计一个函数模板，实现两数的交换，并用int、float、char等类型的数据进行测试

下面是一个使用函数模板实现两数交换的例子：

#include <iostream>
using namespace std;

template <typename T>
void swap(T& a, T& b)
{
    T temp = a;
    a = b;
    b = temp;
}

int main()
{
    int x = 1, y = 2;
    float a = 1.5, b = 2.5;
    char c1 = 'a', c2 = 'b';

    cout << "Before swap: x=" << x << ", y=" << y << endl;
    swap(x, y);
    cout << "After swap: x=" << x << ", y=" << y << endl;

    cout << "Before swap: a=" << a << ", b=" << b << endl;
    swap(a, b);
    cout << "After swap: a=" << a << ", b=" << b << endl;

    cout << "Before swap: c1=" << c1 << ", c2=" << c2 << endl;
    swap(c1, c2);
    cout << "After swap: c1=" << c1 << ", c2=" << c2 << endl;

    return 0;
}

输出结果为：

Before swap: x=1, y=2
After swap: x=2, y=1
Before swap: a=1.5, b=2.5
After swap: a=2.5, b=1.5
Before swap: c1=a, c2=b
After swap: c1=b, c2=a

可以看到，通过函数模板实现的swap函数可以用于多种类型的数据，并且能够达到正确的交换效果。