Question

我有一个文件，其中包含逐行存储的浮点数。示例：

我希望程序逐行读取文件并将此数字作为字符串存储在向量中，然后将其转换为长双精度。我写了这段代码：

#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <vector>

using namespace std;
int main()
{
int j = 0;
cout.precision(16);
string s, weights;

cout << "You need to enter the filename of the file containing weights." << endl;
cout << "ENTER weights filename: ";
cin >> weights;
cout << endl;

ifstream weightsfile;
weightsfile.open(weights.c_str());

vector <string> weights_s;
vector <long double> weights_ld;

while(weightsfile >> j) // this loop reads weights from file
{
    getline (weightsfile, s);
    weights_s.push_back(s);
}

for(j = 0; j < weights_s.size(); j++) // this loop converts string data to long doubles and gives the output
    {
        weights_ld.push_back(strtold(weights_s[j].c_str(), NULL));
        cout << weights_s[j] << endl;
        cout << weights_ld[j] << endl;
    }

weightsfile.close();

return 0;
}

那是什么问题？输出为：

我想我的程序会跳过小数点前的数字。我该怎么做才能解决此问题？

Answer 1

while(weightsfile >> j)

从每行的开头读取一个整数，您对getline的调用然后读取该行的其余部分。

while(getline(weightsfile, s))
{
    weights_s.push_back(s);
}

会有理想的效果。

您实际上是否需要字符串列表？您能立即转换为双打吗（通过一些额外的错误检查）：

while(getline(weightsfile, s))
{
    size_t pos;
    weights_ld.push_back(std::stold(s, &pos));
    if (pos != s.size())
    {
       throw std::invalid_argument("invalid weight");
    }
}

逐行读取浮点数

1 个答案: