Hi everybody. I hope nobody is working too hard.

I am trying to figure out a way to use the peek() method of the stringstream class but looking
more than one place forward.

For example, if I use stringstream.peek() it will let me know the value one value ahead of the current cursor position. Can I check 2 or 3 positions ahead of the cursur without actually moving the cursure such as when you use seekg()?


The reason for the limited amount of "peeking" is because certain types of streams cannot accomodate more than a single character peeking (and no seeking). But for the streams that can easily support moving back-and-forth (seeking) in the underlying data, there is no reason to use peek() instead of the tellg / seekg method. For instance, file-streams can accomodate seeking around the data, although it's preferrable to read/write sequentially or seek as little as possible. In the case of string-streams, they support seeking around the data with ease, and there is essentially no significant cost to seeking back-and-forth anywhere in the data.

So, don't use "peek", use the tellg/seekg method, as so, for example:

std::string peek_next_word(std::istream& in) {
  std::string result;
  std::streampos p_orig = in.tellg();
  in >> result;
  return result;

Basically, any kind of implementation of a multi-character peeking function would have to use a mechanism similar to the above code (tellg / read / seekg) and that's why there is no reason to have a separate function (e.g., "peek_n(str,n);") in the standard streams to do this, because it's not gonna be more efficient than this tellg-seekg method.

This question has already been answered. Start a new discussion instead.