读取字符串和双精度

reading in strings and doubles

本文关键字：双精度 字符串 读取      更新时间：2023-10-16

我遇到了一个问题，从文件中读取字符串，然后从文件中读取double。我的教授建议我在每个输入行后面放一个特殊的getline，但是它不起作用，我推断这是程序的问题。有没有更简单的双打方式?

输入文件的例子是:

John Smith
019283729102380
300.00
2000.00
Andrew Lopez
293481012100121
400.00
1500.00

代码如下:

while(! infile.eof())
{
getline(infile,accname[count],'n');
getline(infile, refuse, 'n');  
getline(infile,accnum[count],'n');
getline(infile, refuse, 'n');  
infile>>currbal[count];  
getline(infile, refuse, 'n');  
infile>>credlim[count];  
getline(infile, refuse, 'n');  
count++;
}

编辑:根据OP的澄清更新。

根据您提供的示例，这应该可以工作:

while(1) {
    std::string s1;
    if(!std::getline(infile, s1))
        break;
    std::string s2;
    if(!std::getline(infile, s2))
        break;
    double d1, d2;
    if(!(infile >> d1 >> d2))
        break;
    accname[count] = s1;
    accnum[count] = s2;
    currball[count] = d1;
    credlim[count] = d2;
    count++;
}

这段代码将适用于如下输入:

Adam Sandler
0112233
5 100
Ben Stein
989898
100000000
1

但是对于像

这样的输入就不起作用了
Adam Sandler
0112233
5 100
Ben Stein
989898
100000000
1

我认为Rob Adams的响应在解析多个记录时有一个小错误。在第一次提取d2之后，示例输入流将包含nBen Steinn989898n100000000n1，因此下一次调用std::getline()将提取空字符串而不是Ben Stein。因此，似乎有必要在每次while循环迭代结束时使用空字符串。

我认为下面的代码示例提供了一个修复: 
#include <iostream>
#include <sstream>
int main(int argc, char** argv) {
  using std::stringstream;
  stringstream infile(stringstream::in | stringstream::out);
  infile << "John Smithn";
  infile << "019283729102380n";
  infile << "300.00n";
  infile << "2000n";
  infile << "Andrew Lopezn";
  infile << "293481012100121n";
  infile << "400.00n";
  infile << "1500.00n";
  std::string account_name;
  std::string account_number;
  double current_balance;
  double credit_limit;
  int count = 0;
  while (std::getline(infile, account_name) &&
         std::getline(infile, account_number) >> current_balance >>
         credit_limit) {
    std::cout << account_name << std::endl;
    std::cout << account_number << std::endl;
    std::cout << current_balance << std::endl;
    std::cout << credit_limit << std::endl;
    /*
    accname[count] = account_name;
    accnum[count] = account_number;
    currball[count] = current_balance;
    credlim[count] = credit_limit;
    */
    count++;
    // Consume the leading newline character, which seprates the credit limit
    // from the next account name, when infile contains multiple records.
    //
    // For example, after consuming the record for John Smith, the stream will
    // contain: "nAndrew Lopezn293481012100121n400.00n1500.00n". If you
    // don't consume the leading newline character, calling std::getline() to
    // parse the next account name will extract an empty string.
    std::string blank;
    std::getline(infile, blank);
  }
  return 0;
}

string str;
while(!infile.eof())
{
    getline(infile, accname[count]);//  you do not need 'n' it will always read to 
                     // end of the line
    getline(infile, accnum[count]);
    getline(infile, str);
    currbal[count] = atof(str.c_str());
    getline(infile, str);
    credlim[count] = atof(str.c_str());
    count++;
}
* 
for the file 
John Smith
019283729102380
300.00
2000.00
Andrew Lopez
293481012100121
400.00
1500.00
*
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