This recipe is the most important recipe in this chapter! Let's take a look at a very common case, where we write some function that accepts a string and returns a part of the string between character values passed in the starts and ends arguments:

#include <string>
#include <algorithm>

std::string between_str(const std::string& input, char starts, char ends) {
    std::string::const_iterator pos_beg 
        = std::find(input.begin(), input.end(), starts);
    if (pos_beg == input.end()) {
        return std::string();
    }
    ++ pos_beg;

    std::string::const_iterator pos_end 
        = std::find(pos_beg, input.end(), ends);

    return std::string(pos_beg, pos_end);
}

Do you like this implementation? In my opinion, it is awful. Consider the following call to it:

between_str("Getting expression (between brackets)", &apos...