stringstream adding an extra zero

Question

I am facing a problem with the below code.

short int decrypted0[] = {0,2};
string message = "22";
string string0 ="";

for(i=0;i<message.size();i++)
{        
     ss<<decrypted0[i];
     string0+=ss.str();     
}

Why does after the second iteration string0 have a value "002" rather than "02"?

I tried with VS and Qt, Same results.

`std::stringstream` is created outside the loop, so it doesn't empty between loop iterations. — LogicStuff, Mar 19 '15 at 20:29
But that's not my logic. What I shown was a sample case, loop may go for 100. Same problem. — Sreeraj Chundayil, Mar 19 '15 at 20:29
Wrong fix: Follow @LogicStuff advice and put the stringsteam in the lloop — , Mar 19 '15 at 20:39
@DieterLücking : http://stackoverflow.com/questions/20731/in-c-how-do-you-clear-a-stringstream-variable see the top rated answer — Sreeraj Chundayil, Mar 19 '15 at 20:42

SirGuy · Accepted Answer · 2015-03-19T20:38:47.377

std::stringstream::str() does not empty the stream, it's more of a snapshot of the current internals. The clear its internal buffer use ss.str("").

This means that your loop gives after the first iteration:

    ss.str() == "0"
    string0 == "0"

and then the after the second iteration you get:

    ss.str() == "02"
    string0 == "002"

Much easier would be to do:

    for(i=0;i<message.size();i++)
         ss<<decrypted0[i];
    string0 = ss.str();

stringstream adding an extra zero

1 Answers1