Why do we need to use a stringstream when splitting a string?

Question

Please note, I've never used streams before today, so my understanding of them remains rather vague. Apologies when I say something appallingly stupid.

Here I have a short bit of code that splits up a stringstream into a bunch of strings at each space.

vector<string> words;
stringstream ss("some random words that I wrote just now");
string word;
while(getline(ss, word, ' ')){
    words.push_back(word);
}

I'm wondering why we're using a stringstream here, rather than just a string .
This would work like:

1. Create a string object at memory location x
2. When referenced, go through each character and check if it is a space. All previous characters should be saved somewhere temporary.
3. If it is a space, grab all the stuff we've just stored and stick it on the end of the vector, then, clear the temp storage thing. If it's not a space, go back to step 2

What's storing "some random words that I wrote just now" as a stringstream going to do to help us here? Is it just making a stream of characters so that we can check through them? Is this necessary? Are we always doing this, even in other languages?

Answer 1

I'm wondering why we're using a stringstream here, rather than just a string.

If this is the question, then one big reason why stringstream is used is simply -- because it works with little effort by the programmer. The less code you write, the less chance for bugs to occur.

Your method of using just std::string and searching for spaces requires the C++ programmer to write all of those steps (create a string, manually search for spaces, etc). It may be trivial to write, but even the best programmers can make mistakes in trivial code. The code may have bugs, may not cover all of the corner cases, etc.

As to ease of use:

When a C++ programmer sees stringstream with respect to usage of separating a sting with whitespace, the purpose of the code is immediately known.

If on the other hand, a programmer decides to manually parse the data by using just string and searching for spaces, the code is not immediately realized as to what it does when another programmer reads the code. Sure, it may be a quick realization of the code by the other programmer, but I can bet the other programmer will say "why didn't you use stringstream?".

Answer 2

What's storing "some random words that I wrote just now" as a stringstream going to do to help us here? Is it just making a stream of characters so that we can check through them? Is this necessary?

std::stringstream just allows you to use the usual input/output operations such as >> and std::getline on a string. You can't use std::getline to read from an std::string , so you put the string in a std::streamstream first. You can totally parse a string by looping over the characters yourself as you described.

Are we always doing this, even in other languages?

Not in Python at least. There you would just do words = line.split(' ') .