从<iostream>收集来自cin的字符串输入并将其转换为double的正确方法是什么？

Question

#include <iostream>
#include <cmath>
#include <fstream>
using namespace std;



//Initializing some variables.

string PairOfAverage = "blank";
string ConsoleInput = "";
double OrderEntry = 0;
double OrderAmount = 0;
double WeightFactor1[] = {};
double WeightFactor2 = 0;
string inputString = "";


int main() {

    cout<< "Do you wish to determine average position for a pair? " << endl;
    cout << "Please answer \"true\" or \"false\"."<< endl;
    cin >> ConsoleInput; 

//在这里你应该输入＆＃34; true＆＃34;或＆＃34; false＆＃34;。

    bool DetermineAverage = ToBool(ConsoleInput); 

    cout << "Please enter the currency pair Symbol in XXXYYY format:";
    cin >> PairOfAverage; 

//在这里你应该输入一个字符串。

    for (int i=0;DetermineAverage==true;i++) {

        cout << "Please enter the order's entry price: ";
        cin >> inputString; 

//这里的输入应该是双倍的。

        OrderEntry = stod (inputString,NULL);
        cout << "Please enter the order's amount: ";
        cin >> inputString; 

//这里的输入应该是双倍的。

        OrderAmount = stod (inputString,NULL);
        sleep(1);
        cout << OrderAmount << " <-- OrderAmount" << endl;
        WeightFactor1[i] = OrderEntry*OrderAmount;
        WeightFactor2 += OrderAmount;
        cout << "weight factor: " << WeightFactor2 << endl;
        cout << "Do you want to introduce more orders for the same pair? " << endl;
        cout << "Please answer \"true\" or \"false\"."<< endl;
        cin >> ConsoleInput; 

//在这里你应该输入＆＃34; true＆＃34;或＆＃34; false＆＃34;。

        DetermineAverage = ToBool(ConsoleInput);

        sleep(1);
        if (DetermineAverage == false) {
            double sum = 0.0;
            for (int j = 0; j <= i ; j++){
                sum+=WeightFactor1[j];
                cout<<"sum equals: " << sum << " " << j << endl;
            }
            double result = sum/WeightFactor2;
            cout<< "Average Price for " << WeightFactor2 << " units of " << PairOfAverage << " is: " << result << endl;

        }
    }
    return 0;
}

//这是一个将字符串解析为bool类型的函数。

bool ToBool(string ConsoleInput){
    bool InputBool ;
    if (ConsoleInput == "false"){
        InputBool = false;
    }
    else if(ConsoleInput == "true"){
        InputBool = true;
    }
    return(InputBool);
}

 //The error I get is the result of variable WeightFactor2. It does not add up
 //the sum of the introduced valued the where passed as string through cin>>
 //and then parsed to double.
 //I hope you can help me on this.

Answer 1

是否有使用转换的原因？您可以读取所需的任何基本类型的输入，因此您可以直接读取bool或double值，例如cin >> OrderAmount。无需字符串转换。

Answer 2

输入流double为overload。

double value;
std::cin >> value;

你去吧。这是将标准输入转换为double。

的规范方法

Answer 3

你需要纠正你对double WeightFactor1 [] = {}的使用来向量＆lt;双＆gt; WeightFactor1;

#include <iostream>
#include <cmath>
#include <fstream>
#include <vector>
using namespace std;



//Initializing some variables.

string PairOfAverage = "blank";
string ConsoleInput = "";
double OrderEntry = 0;
double OrderAmount = 0;
vector< double > WeightFactor1;
double WeightFactor2 = 0;
string inputString = "";

bool ToBool(string ConsoleInput){
    bool InputBool ;
    if (ConsoleInput == "false"){
        InputBool = false;
    }
    else if(ConsoleInput == "true"){
        InputBool = true;
    }
    return(InputBool);
}


int main() {

    cout<< "Do you wish to determine average position for a pair? " << endl;
    cout << "Please answer \"true\" or \"false\"."<< endl;
    cin >> ConsoleInput; 
//Here you should input "true" or "false".

    bool DetermineAverage = ToBool(ConsoleInput); 

    cout << "Please enter the currency pair Symbol in XXXYYY format:";
    cin >> PairOfAverage; 
//Here you should input a string.

    for (int i=0;DetermineAverage==true;i++) {

        cout << "Please enter the order's entry price: ";
        cin >> OrderEntry;
//Here input should be a double.

        cout << "Please enter the order's amount: ";
        cin >> OrderAmount;
//Here input should be a double.

        //sleep(1);
        cout << OrderAmount << " <-- OrderAmount" << endl;
        WeightFactor1.push_back( OrderEntry*OrderAmount );
        WeightFactor2 += OrderAmount;
        cout << "weight factor: " << WeightFactor2 << endl;
        cout << "Do you want to introduce more orders for the same pair? " << endl;
        cout << "Please answer \"true\" or \"false\"."<< endl;
        cin >> ConsoleInput; 
//Here you should input "true" or "false".

        DetermineAverage = ToBool(ConsoleInput);

        //sleep(1);
        if (DetermineAverage == false) {
            double sum = 0.0;
            for (int j = 0; j <= i ; j++){
                sum+=WeightFactor1[j];
                cout<<"sum equals: " << sum << " " << j << endl;
            }
            double result = sum/WeightFactor2;
            cout<< "Average Price for " << WeightFactor2 << " units of " << PairOfAverage << " is: " << result << endl;

        }
    }
    return 0;
}
//This is a function to parse the string to bool type.


 //The error I get is the result of variable WeightFactor2. It does not add up
 //the sum of the introduced valued the where passed as string through cin>>
 //and then parsed to double.
 //I hope you can help me on this.