user584583 user584583 - 6 days ago 6
C++ Question

stringstream string to int

The C++ code below does

int
to
string
and a
string
to
int
conversions. Then, it repeats these steps again. The
stringstream
to
int
line
stream1 >> i3;
is breaking the code. What am I missing here?

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

int main()
{
int i1 = 101;
int i2 = 202;
int i3 = 0;
string s1 = "";
string s2 = "";
stringstream stream1;

for (int i=0;i<2;i++)
{

//int to string
stream1.str("");
cout << "i1 " << i1 << endl;
stream1 << i1;
s1 = stream1.str();
cout << "s1 " << s1 << endl;

//int to string
cout << "i2 " << i2 << endl;
stream1.str("");
stream1 << i2;
s2 = stream1.str();
cout << "s2 " << s2 << endl;

//string to int
stream1.str("");
stream1.str(s2);
stream1 >> i3;
//line above causes s1 and s2 to get messed up during 2nd time in for loop
cout << "i3-- " << i3 << endl;

}
return 0;
}

Answer

I tested your code and could reproduce the problem. I solved it inserting a .clear() before .str("")

Have a look here: How to reuse an ostringstream?

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

int main()
{
 int i1 = 101;
 int i2 = 202;
 int i3 = 0;
 string s1 = "";
 string s2 = "";
 stringstream stream1;

 for (int i=0;i<2;i++)
 {

   //int to string
   stream1.clear();
   stream1.str("");
   cout << "i1 " << i1 << endl;
   stream1 << i1;
   s1 = stream1.str();
   cout << "s1 " << s1 << endl;

   //int to string
   cout << "i2 " << i2 << endl;
   stream1.clear();
   stream1.str("");
   stream1 << i2;
   s2 = stream1.str();
   cout << "s2 " << s2 << endl;

   //string to int
   stream1.clear();
   stream1.str("");
   stream1.str(s2);
   stream1 >> i3;
   //line above causes s1 and s2 to get messed up during 2nd time in for loop
   cout << "i3-- " << i3 << endl;

  }
  return 0;
 }
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