CODEWITHSUNDEEP
c++stringstream
jackhab
jackhab

Reputation: 17718

Stringstream extract integer

Why do I fail to extract an integer value into the Num variable?

#include <sstream>
#include <vector>
#include <iostream>

using namespace std;

int main()
{
    string Digits("1 2 3");
    stringstream ss(Digits);
    string Temp;
    vector<string>Tokens;

    while(ss >> Temp)
        Tokens.push_back(Temp);

    ss.str(Tokens[0]);

    int Num = 0;
    ss >> Num;
    cout << Num;    //output: 0
}

Upvotes: 10

Views: 13998

Answers (4)

Logan Capaldo
Logan Capaldo

Reputation: 40346

STL! :P

stringstream ss("1 2 3");
vector<int> Tokens;
copy(istream_iterator<int>(ss), istream_iterator<int>(), back_inserter(Tokens));

Upvotes: 4

Johannes Schaub - litb
Johannes Schaub - litb

Reputation: 507403

You have to reset all status flags (eofbit) and bring the stream into a good state (goodbit):

ss.clear(); // clear status flags
ss.str(Tokens[0]);

The reason is that if you keep extracting until the end, you will hit the end, and the eof flag will be set on that stream. After that, read operations will be canceled and you have to clear that flag out again. Anyway, after clearing and resetting the string, you can then go on extracting the integers.

Upvotes: 7

anon
anon

Reputation:

When the stream extracts the last of the 3 digist "1 2 3" the eof state will be set. This is not cleared by the str() member,you need to do it yourself. Change your code to:

ss.clear();
ss.str(Tokens[0]);

Upvotes: 12

Assaf Lavie
Assaf Lavie

Reputation: 76153

Why are you reading into a temp string variable?

You can just read from the stringstream into an int...

int main()
{
    string Digits("1 2 3");
    stringstream ss(Digits);
    int Temp;
    vector<int> Tokens;

    while(ss >> Temp)
        Tokens.push_back(Temp);
}

Upvotes: 8

Related Questions