处理输入和输出的C++函数

Question

我接到一个任务，用C++编写代码，我必须开发一个算法，检查3个数字在以下标准，如果第一数字指数第二数字等于第三数字，那么它应该返回真或假。我利用power函数找到第一个数字上升到第二个数字，另一个函数叫做comapare(num1,num2,num3).My pogramme工作正常，但问题是它在一个控制台显示结果，我想输出到一个输出文件，我命名为outfile，当我这样做，我得到一个错误，说outfile没有声明，我将感激任何帮助能够输出到输出文件。 以下是我的代码

#include <iostream>
#include<fstream>

using namespace std;

double powerfunc(double num1,double num2){ // power function  

    double base=num1,exponent=num2,result;//decalsring base and exponent

    for(int i=1;i<exponent;i++){
        base=base*base;
        result=base;
    }
    return result;
}

double compare(double x, double y,double z){//Comapares if x exponent y gives z and return 
    //Return true or false

    int storersults;
    if( (powerfunc(x,y)== z)){
        cout<<"true"<<endl;
        //outfile<<"true"<<endl;
        storersults=powerfunc(x,y);
        cout<<"results is "<<storersults;
        //outfile<<"results is "<<storersults;
    }
    else{
        cout<<"false"<<endl;
        //outfile<<"false"<<endl;
        storersults=powerfunc(x,y);
        cout<< " results is "<<storersults;
        //outfile<<"results is "<<storersults;
    }
    return storersults;
}

int main(){
    ifstream infile;
    ofstream outfile;

    infile.open(" input.txt");
    outfile.open("output.txt");// I wanna link output to functions above and get results // I wann get results on outputfile not on console
    // double a,b,c;
    //infile>>a,b,c;
    powerfunc(3,2);//This functions finds power of 3 and 2
    compare(3,2,9);//This fucnions compare if 3^2=9 then retuens true

    }
    infile.close();
    outfile.close();
    return 0;
}

Answer 1

你可以在要输出的函数中接受输出流，像这样。

double compare(double x, double y,double z, std::ostream &out) {
                                          // ^^^ accept some stream
  out << "hello"; // print whatever output to the stream
}

然后在 main你可以这样调用它。

outfile.open("output.txt");
compare(3,2,9, std::cout);   // to print to console
compare(3,2,9, outfile);     // to print to file

Answer 2

我得到一个错误，说outfile没有声明。

因为 outfile 外用 main()

你犯了一个语法错误。去掉那个括号

int main(){
    ifstream infile;
    ofstream outfile;

    infile.open(" input.txt");
    outfile.open("output.txt");// I wanna link output to functions above and get results // I wann get results on outputfile not on console
    // double a,b,c;
    //infile>>a,b,c;
    powerfunc(3,2);//This functions finds power of 3 and 2
    compare(3,2,9);//This fucnions compare if 3^2=9 then retuens true

} // <- main() ends here
    infile.close();
    outfile.close();
    return 0;
}