我的功能有什么问题？

Question

我对c++相当陌生，并且正在处理各种函数。我似乎不明白为什么下面的代码不工作，任何帮助都会非常感激。

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

int main() {
    movieOutput("Hello");

    return 0;
}

//This is just for a little extra versatility
int movieOutput(string movieName,int aTix = 0,int cTix = 0,float grPro = 0.0,float nePro = 0.0,float diPro = 0.0){

    //I don't understand whether I should declare the arguments inside the 
    //functions parameters or in the function body below.

    /*string movieName;
      int aTix = 0, cTix = 0;
      float grPro = 0.0, nePro = 0.0, diPro = 0.0;*/

    cout << "**********************Ticket Sales********************\n";
    cout << "Movie Name: \t\t" << movieName << endl;
    cout << "Adult Tickets Sold: \t\t" << aTix << endl;
    cout << "Child Tickets Sold: \t\t" << aTix << endl;
    cout << "Gross Box Office Profit: \t" << grPro << endl;
    cout << "Net Box Office Profit: \t" << nePro << endl;
    cout << "Amount Paid to the Distributor: \t" << diPro << endl;

    return 0;
}

我得到的构建错误

`Build:(compiler: GNU GCC Compiler)
|line-8|error: 'movieOutput' was not declared in this scope|
Build failed: 1 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|`

Answer 1

你提交了一份声明

int movieOutput(string movieName,int aTix = 0,int cTix = 0,
                float grPro = 0.0,float nePro = 0.0,float diPro = 0.0);

出现在main()前。

此外，默认参数需要放在函数声明中，而不是定义签名中。

这是固定代码：

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

int movieOutput(string movieName,int aTix = 0,int cTix = 0,
                float grPro = 0.0,float nePro = 0.0,float diPro = 0.0);

int main() {
    movieOutput("Hello");

    return 0;
}

//This is just for a little extra versatility
int movieOutput(string movieName,int aTix,int cTix,float grPro,float nePro,float diPro){

    cout << "**********************Ticket Sales********************\n";
    cout << "Movie Name: \t\t" << movieName << endl;
    cout << "Adult Tickets Sold: \t\t" << aTix << endl;
    cout << "Child Tickets Sold: \t\t" << aTix << endl;
    cout << "Gross Box Office Profit: \t" << grPro << endl;
    cout << "Net Box Office Profit: \t" << nePro << endl;
    cout << "Amount Paid to the Distributor: \t" << diPro << endl;

    return 0;
}

Answer 2

只需在调用x之前声明函数即可)

int movieOutput(string, int, int, float, float, float); // function prototype 

int main()... 

int movieOutput(...) { /* declaration goes here */} 

或者简单地将整个函数声明放在主程序前面。