Simple coroutine string parser

In this section, we will implement our last example: a simple string parser. The coroutine will wait for the input, a std::string object, and will yield the output, a number, after parsing the input string. To simplify the example, we will assume that the string representation of the number doesn’t have any errors and that the end of a number is represented by the hash character, #. We will also assume that the number type is int64_t and that the string won’t contain any values out of that integer type range.

The parsing algorithm

Let’s see how to convert a string representing an integer into a number. For example, the string "-12321#" represents the number -12321. To convert the string into a number, we can write a function like this:

int64_t parse_string(const std::string& str) {
    int64_t num{ 0 };
    int64_t sign { 1 };
    std::size_t c = 0...