。函数指针数组。不懂错误的意思

#include<iostream>
using namespace std;
void square(float &x, float &y)
{
    x=x*x;
    y=y*y;
}
void cube(float &x, float &y)
{
    x=x*x*x;
    y=y*y*y;
}
void print(float &x, float &y)
{
    cout<<"长："<<x<<"\t"<<"宽："<<y<<endl;
}
void swap(float &x, float &y)
{
    float z;
    z=x;
    x=y;
    y=z;
}
int main(void)
{
    float a=2,b=3;
    char choice='0';
    int i;
    void (*p[5])(float &, float &);
    for (i=0; i<5; i++)
    {
        bool quit = false;
        cout<<"(0)退出，(1)平方，(2)立方，(3)交换x和y的值：";
        cin>>choice;
        switch (choice)
        {
        case '0': quit=true;    break;
        case '1': p[i]=square;    break;
        case '2': p[i]=cube;    break;
        case '3': p[i]=swap;    break;                //错误指向的地方
        default:p[i]=0;
        }
        if (quit)break;
        if (p[i]==0)
        {
            cout<<"请输入0到3之间的数字：";
            i=i-1;
            continue;
        }
        cout<<"第"<<i<<"次执行，到第5次结束\n";
        cout<<"初始值\n";
        print(a,b);
        cout<<"现在调用函数指针数组p["<<i<<"]所指向的函数...\n";
        p[i](a,b);
        cout<<"运算后\n";
        print(a,b);
    }
    return 0;
}
/*
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E:\c++\108函数指针数组\01.cpp(40) : error C2563: mismatch in formal parameter list
E:\c++\108函数指针数组\01.cpp(40) : error C2568: '=' : unable to resolve function overload
        could be 'void __cdecl swap(float &,float &)'
        E:\c++\108函数指针数组\01.cpp(17) : see declaration of 'swap'
        or       'void __cdecl std::swap(float &,float &)'
        d:\vc98\include\xutility(99) : see declaration of 'swap'
        or       'void __cdecl std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >::swap(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &,class std::basic_string<char,struct std:
:char_traits<char>,class std::allocator<char> > &)'
        d:\vc98\include\xstring(378) : see declaration of 'swap'
        or       'void __cdecl std::swap(_Ty &,_Ty &)'
        d:\vc98\include\xutility(99) : see declaration of 'swap'
Error executing cl.exe.

01.obj - 2 error(s), 0 warning(s)
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*/