Question

我正在编写一个涉及多个文件的示例示例。详细代码如下。

的main.cpp

#include <algorithm>
#include <iomanip>
#include <ios>
#include <iostream>
#include <stdexcept>
#include <string>
#include <vector>
#include "grade.h"
#include "Student_Info.h"

using std::cin;
using std::cout;
using std::domain_error;
using std::endl;
using std::max;
using std::setprecision;
using std::sort;
using std::streamsize;
using std::string;
using std::vector;

int main()
{
    vector<Student_Info> students;
    Student_Info record;
    string::size_type maxlen = 0;       //the length of the longest name

    //read and store all the student's data
    //Invariant: students contains all the student records read so far
    //maxlen contains the length of the longest name in students
    while(read(cin,record))
    {
        //find length of the longest name
        maxlen=max(maxlen,record.name.size());
        students.push_back(record);
    }

    //alphabetize the student records
    sort(students.begin(),students.end(),compare);

    //write the names and grades
    for(vector<Student_Info>::size_type i=0; i!=students.size();++i)
    {
        //write the name, padded to the right to maxlen + 1 characters
        cout << students[i].name << string(maxlen+1-students[i].name.size(),' ');

        //compute and write the grade
        try
        {
            double final_grade=grade(students[i]);
            streamsize prec = cout.precision();
            cout << setprecision(3) << final_grade << setprecision(prec);
        }
        catch(domain_error e)
        {
            cout << e.what();
        }

        cout << endl;
    }

    return 0;
}

Student_info。{H，CPP}

#ifndef GUARD_Student_Info
#define GUARD_Student_Info

#include <iostream>
#include <string>
#include <vector>

using std::iostream;
using std::string;
using std::vector;

struct Student_Info
{
    std::string name;
    double midterm,final;
    std::vector<double> homework;
};

bool compare(const Student_Info&, const Student_Info&);
std::istream& read(std::istream&, Student_Info&);
std::istream& read_hw(std::istream&, std::vector<double>&);

#endif
#include "Student_Info.h"

using std::istream;
using std::vector;

bool compare(const Student_Info& x, const Student_Info& y)
{
    return x.name < y.name;
}

istream& read(istream& is, Student_Info& s)
{
    is >> s.name >> s.midterm >> s.final;

    read_hw(is,s.homework); //read and store all the students' homework grades
    return is;
}

istream& read_hw(istream& in, vector<double>& hw)
{
    if(in)
    {
        //get rid of previous contents
        hw.clear();

        //read homework grades
        double x;
        while(in>>x)
         hw.push_back(x);

        //clear the stream so that the input would work for the next student
        in.clear();
    }

    return in;
}

级。{H，CPP}

#ifndef GRADE_H
#define GRADE_H

//grade.h
#include <vector>
#include "Student_Info.h"

double grade(double,double,double);
double grade(double,double,const std::vector<double>&);
double grade(const Student_Info&);

#endif

#include <stdexcept>
#include <vector>

#include "median.h"
#include "grade.h"


double grade(const Student_Info& s)
{
    return grade(s.midterm,s.final,s.homework);
}

double grade(double midterm, double final, const vector<double>& hw)
{
    if(hw.size()==0)
        throw domain_error("student has done no homework");
    return grade(midterm, final, median(hw));
}

double grade(double midterm,double final,double homework)
{
    return 0.2*midterm + 0.4*final + 0.4*homework;
}

中位数。{H，CPP}

#ifndef MEDIAN_H
#define MEDIAN_H

#include <vector>           
#include <stdexcept>        //to get the declaration of domain_error
#include <algorithm>        //to get the declaration of sortt

using std::domain_error;
using std::sort;
using std::vector;

double median(std::vector<double>);

#endif
#include "median.h"

double median(vector<double> vec)
{
    typedef vector<double>::size_type vec_sz;

    vec_sz size=vec.size();
    if(size==0)
        throw domain_error("median of an empty vector");
    sort(vec.begin(),vec.end());

    vec_sz mid=size/2;

    return size%2==0 ? (vec[mid]+vec[mid-1])/2:vec[mid];
}

问题是当我在linux上使用g ++编译它并运行./a.out时没有任何反应。这很奇怪。我已经完成了代码，但找不到任何不妥之处。希望有人能找到故障。

Answer 1

通过“没有任何反应”，你的意思是它在等待输入并且不会退出吗？

while(read(cin,record))对我来说肯定是这样的。通过标准输入传递内容。

Answer 2

通过目视检查发现错误通常很困难 - 在我们的例子中，特别是因为我们仍然没有完整的代码（尽管你发布了重要部分）。

你应该学习使用GNU调试器gdb。使用g++ -g编译您的程序，然后运行gdb a.out。然后，我建议使用以下命令：

b main（在main上设置断点）
r（启动程序，停在主程处）
s（程序的单步，所以你可以看到为什么它没有做任何事情）

Answer 3

您是否提供意见？该程序期望从标准输入读取一系列Student_Info记录。如果你有一个包含学生记录的文件，你需要有一个命令行：

./a.out < student_records.txt

运行可执行文件什么都不做

3 个答案: