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How to extract mixed format using istringstream

Why is my program not displayed:

10
1.546
,Apple 1

instead

10
1
<empty space>

here is my program:

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main () {
    string str = "10,1.546,Apple 1";
    istringstream stream (str);
    int a;
    double b;
    string c, dummy;
    stream >> a >> dummy >> b >> dummy >> c;
    cout << a << endl;
    cout << b << endl;
    cout << c << endl;
    return 0;
}

Basically I am trying to parse strings separated by commas, any smoother way to do this will help me unlimitedly.

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4 answers

IOStreams ( C-, ++) . , , . , , , , , : dummy , .

, char , . Apple 1 , , operator>>() . std::getline():

string c;
char dummy;

if ((stream >> a >> dummy >> b >> dummy) &&
     std::getline(stream >> std::ws, s))
//   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
{

}

, std::ws . if, , , .

.

, std::ctype<char> , . . :

namespace detail
{
    enum options { add, remove };

    class ctype : public std::ctype<char>
    {
    private:
        static mask* get_table(const std::string& ws, options opt)
        {
            static std::vector<mask> table(classic_table(),
                                           classic_table() + table_size);
            for (char c : ws)
            {
                if (opt == add)
                    table[c] |= space;
                else if (opt == remove)
                    table[c] &= ~space;
            }
            return &table[0];
        }
    public:
        ctype(const std::string& ws, options opt)
            : std::ctype<char>(get_table(ws, opt)) { }
    };
}

class adjustws_impl
{
public:
    adjustws_impl(const std::string& ws, detail::options opt) :
        m_ws(ws),
        m_opt(opt)
    { }

    friend std::istream& operator>>(std::istream& is,
                                    const adjustws_impl& manip)
    {
        const detail::ctype* facet(new detail::ctype(manip.m_ws, manip.m_opt));

        if (!std::has_facet<detail::ctype>(is.getloc())
        {
            is.imbue(std::locale(is.getloc(), facet));
        } else
            delete facet;

        return is;
    }
private:
    std::string m_ws;
    detail::options m_opt;
};

adjustws_impl setws(const std::string& ws)
{
    return adjustws_impl(ws, detail::add);
}

adjustws_impl unsetws(const std::string& ws)
{
    return adjustws_impl(ws, detail::remove);
}

int main()
{
    std::istringstream iss("10,1.546,Apple 1");
    int a; double b; std::string c;

    iss >> setws(","); // set comma to a whitespace character

    if ((iss >> a >> b) && std::getline(iss >> std::ws, c))
    {
        // ...
    }

    iss >> unsetws(","); // remove the whitespace classification
}
+4

.

" ", cin/cout "", imho.

, , .

 int main (int, char**)
 {
    // always initialize your variables 
    // to value you would not expect from input        
    int            a = -99;
    double         b = 0.0;
    std::string    c("");
    char comma1 = 'Z';
    char comma2 = 'z';

    std::string str = "10,1.546,Apple 1";
    std::istringstream ss(str);

    ss >> a >> comma1 >> b >> comma2;

    // the last parameter has the default delimiter in it
    (void)getline(ss, c, '\n');  // to get past this default delimiter, 
                                 // specify a different delimiter

    std::cout << std::endl;
    std::cout << a << "   '" << comma1 <<  "'   " << std::endl;
    std::cout << b << "   '" << comma2 <<  "'   " << std::endl;
    std::cout << c << std::endl;

    return 0;
 }

: (, , .)

10 ','
1,546 ','
Apple 1

+7

:

string str = "10  1.546 Apple 1";


 stream >> a >> b >> dummy >> c;

In your example, the dummy would have the string "1.546, Apple". Since before the appearance of a non-numeric char, it is passed to the variable a. After that, everything is added to the dummy (string) until the default delimiter (space) is reached

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I managed to change the code a bit. Not yet implemented the method 0x499602D2, but here's what worked for me.

#include <iostream>
#include <string>
#include <cstdlib>
#include <sstream>

using namespace std;

int main () {
    string str = "10,1.546,Apple 1";
    istringstream stream (str);
    int a;
    double b;
    string c;
    string token;
    while (getline (stream, token, ',')) {
        if (token.find (".") == string::npos && token.find (" ") == string::npos) {
            a = atoi (token.c_str ());
        } else if (token.find (".") != string::npos) {
            b = atof (token.c_str ());
        } else {
            c = string (token);
        }
    }
    cout << a << endl;
    cout << b << endl;
    cout << c << endl;
    return 0;
}
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