c++提示错误：'plural' followed by 'int' is illegal (did you forget a ';'?)

#include<iostream>
using namespace std;
#include "function.h"

int main()
{
    plural f(4.5);   
    plural x(2.1,3.2);
    float a=2.3;
    f.add(x);
    f.printf();
    f.add(a);
    f.printf();
    f.subtract(x);
    f.printf();
    f.multiply(x);
    f.printf();
    return 0;
}
plural 是复数类
提示的错误：
function.cpp
C:\Users\qq\Desktop\function.cpp(5) : error C2628: 'plural' followed by 'int' is illegal (did you forget a ';'?)
C:\Users\qq\Desktop\function.cpp(8) : warning C4305: 'argument' : truncation from 'const double' to 'const float'
C:\Users\qq\Desktop\function.cpp(8) : warning C4305: 'argument' : truncation from 'const double' to 'const float'
C:\Users\qq\Desktop\function.cpp(9) : warning C4305: 'initializing' : truncation from 'const double' to 'float'
执行 cl.exe 时出错.