为什么在读取双打和字符串时，istream.clear（）删除部分字符串？ [英] Why is istream.clear() removing part of my strings while reading doubles and strings?

问题描述

我正在读取一个文本文件，该文件由名称和等级组成，格式为：

I am reading a text file consisting of names and grades with the format:

Polly 95 99 95 94 93 98 99 
Abraham 80 85 81 86 95 78 81 

我使用以下代码阅读每个学生转换为Student_info结构：

I use the following code to read each student into a Student_info struct:

// read homework grades from an input stream into a vector<double>
istream& read_hw(istream& in, vector<double>& hw)
{
    if (in)
    {
        // get rid of previous content
        hw.clear();

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

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

    }
    return in;
}

istream& read(istream& in, Student_info& s)
{
    // read and store the student's name, midterm, and final
    in >> s.name >> s.midterm >> s.final;
    //std::cout << "The name is " << s.name << std::endl;

    read_hw(in, s.homework);
    return in;
}

后来我打印了每个学生的姓名和总成绩，但还是有些奇怪。而不是得到

Later on I print each student's name and overall grade, but something strange happens. Instead of getting

Polly 96.6
Abraham 82.2

第一个（Polly）之后的每个名称都被部分切除：

each of the names after the first (Polly) is partially cut off:

Polly 96.6
raham 82.2

我相信这与清除流为下一个学生准备：

I believe it has something to do with clearing the stream to ready it for the next student:

in.clear();

这似乎扔掉了下一个学生名字的开头，但是我不能只是删除此行，因为istream需要返回到OK状态。

It seems to be throwing away the beginning of the next student's name, but I can't just get rid of this line, because the istream needs to return to an OK state.

我如何完成这项任务，但要确保我不会丢掉每个学生姓名的一部分？ （我假设我可能事先不知道有多少作业，所以我不能简单地读6个双打然后继续前进。）

How can I accomplish this task but make sure I don't throw away part of each student's name? (I am assuming I may NOT know how many homework assignments there are beforehand, so I can't simply read 6 doubles and then move on.)

推荐答案

我如何完成此任务，但要确保不丢掉每个学生姓名的一部分？

How can I accomplish this task but make sure I don't throw away part of each student's name?

std::string line;
if (getline(in, line))
{
    std::istringstream iss(line);
    while (iss >> grade)
        hw.push_back(grade);
}

这是一种更加结构化的方法，要求在当前行中列出数字。

This is a more structured approach requiring the numbers be listed on the current line.

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