Thread: Understanding istringstream

Consider I have a vector of strings and then I use an istringstream to read each word of each element in the vector, why do I nescessarily use an istringstream?

This is the code that does what I just described (I think)..

Code:

for(auto &elem : svec)    {
        istringstream strm(elem);
        while (strm >> word)
            //Magic
    }

What would be the equivalent of using something else than an istringstream in this scenario and how does the istringstream work?
Thanks in advance!!
PS. point out any error in the code or improvements if you want..

istringstream is a stream that instead of reading from a file, reads from a supplied string. Otherwise, it is equivalent to reading from files (since we dealing with the stream interface).
You don't necessarily have to use it here. The other alternative would be to to find each space with a find function, then extract it using a substring function. This is another way of doing it.

Aah, that was what I thought, that istringstream is basically fstream, just specifically for strings. (If it's that what you meant) I just wasnt sure. Thank you very much!

Originally Posted by Iceboxes

Aah, that was what I thought, that istringstream is basically fstream, just specifically for strings.

Not quite. istringstream is a specialised istream. fstream and ifstream are other distinct specialisations of istream.

In other words, fstream and istringstream are siblings (in the sense of both being specialisations of istream). But istringstream is not an fstream (nor vice versa).

Originally Posted by Iceboxes

Aah, that was what I thought, that istringstream is basically fstream, just specifically for strings. (If it's that what you meant) I just wasnt sure. Thank you very much!

They're all streams.
fstream is a stream for files.
stringstream is a stream for strings.
std::cout, std::cin are streams for reading and writing to standard input/output (usually the screen and keyboard, but does not necessarily need to be).

that istringstream is basically fstream, just specifically for strings

I meant as in how they work Or do they work differently? If I were to take a fstream, make it into a string and then apply that string to istringstream, I would basically have the same stream as I originally did, just a istringstream instead of a fstream?

If you take the entire contents of a file, put it into a string and make a stringstream from that, it would behave exactly the same as if you were reading directly from the file, yes.