Question

In my code there is a loop that adds sth like that “number,” to stringstream. When it ends, I need to extract ‘,’ add ‘}’ and add ‘{‘ if the loop is to repeated.

I thought i can use ignore() to remove ‘,’ but it didn’t work. Do you know how I can do what I describe?

example:

douCoh << '{';
for(unsigned int i=0;i<dataSize;i++)
  if(v[i].test) douCoh << i+1 << ',';
douCoh.get(); douCoh << '}';

Answer 1

You can extract the string (with the str() member), remove the last char with std::string::erase and then reset the new string as buffer to the std::ostringstream.

However, a better solution would be to not insert the superfluous ',' in the first place, by doing something like that :

std::ostringstream douCoh;
const char* separator = "";

douCoh << '{';
for (size_t i = 0; i < dataSize; ++ i)
{
  if (v[i].test)
  {
    douCoh << separator << i + 1;
    separator = ",";
  }
}
douCoh << '}';