将价格（例如，89.95美元）读入两倍

Ross Satchell 发表于 Dev

罗斯·萨切尔

我正在做一项作业，要求我从txt文件中读取数据。数据字段用于书籍，因此我具有标题，书籍ID，价格，数量。除了阅读价格外，其他一切都运行良好。我正在使用atof（），当我从价格的前面删除“ $”符号时可以使用该功能，但是当“ $”在其中时返回“ 0”。

如何使其忽略“ $”？

txt文件的示例：

Introduction to programming languages
1
$89.99
100

到目前为止，这是我的代码：

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>       


using namespace std;

int main() {
    char title[50];
    char strBookid[10];
    char strPrice[10];
    char strAmount[10];
    int bookId;
    double price;
    int amount;
    ifstream filein("bookfile.txt");

    filein.getline(title, 50);
    cout << "Title : " << title << endl;
    filein.getline(strBookid, 10);
    cout << "BookId as a string : " << strBookid << endl;
    filein.getline(strPrice, 10);
    cout << "Price as a string : " << strPrice << endl;
    filein.getline(strAmount, 10);
    cout << "Qty as a string: " << strAmount << endl;

    bookId = std::atoi(strBookid);
    cout << "The Book ID as an int : " << bookId << endl;
    price = std::atof(strPrice);
    cout << "The price as a double : " << price << endl;


  return 0;
}

怀念

您会发现，C ++标准背后的人们都热爱金钱，并且他们知道我们都这样做，因此他们提出了一种很好的方式来以通用方式在C ++中读取金钱。 std::get_money

你可以这样做：

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>   
#include <locale>    //add this    


using namespace std;

int main() {
    char title[50];
    char strBookid[10];
    char strPrice[10];
    char strAmount[10];
    int bookId;
    long double price;   //changed! get_money only supports long double
    int amount;
    ifstream filein("bookfile.txt");

    filein.getline(title, 50);
    cout << "Title : " << title << endl;
    filein.getline(strBookid, 10);
    cout << "BookId as a string : " << strBookid << endl;

    filein.imbue(std::locale("en_US.UTF-8"));      /// added
    filein >> std::get_money(price);               ///changed
    price /= 100;         //get_money uses the lowest denomination, in this case cents, so we convert it $ by dividing the value by 100
    cout << "Price as a string : $" << price << endl;    ///changed

    filein.getline(strAmount, 10);
    cout << "Qty as a string: " << strAmount << endl;

    bookId = std::atoi(strBookid);
    cout << "The Book ID as an int : " << bookId << endl;
    price = std::atof(strPrice);
    cout << "The price as a double : " << price << endl;


  return 0;
}

作为第二种选择，您可以修改原始代码以$手动测试符号...（请参见下面的代码段）

    ......many lines skipped ...........

    bookId = std::atoi(strBookid);
    cout << "The Book ID as an int : " << bookId << endl;
    price = std::atof(strPrice[0] == '$' ? strPrice+1 : strPrice );   //modified
    cout << "The price as a double : " << price << endl;


  return 0;
}

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