Express one of multiple options in a nice way

We often find ourselves writing if statements where a variable is compared with several values either to check if it matches one of them or that it doesn’t match any. Here is an example:

int option = ...;

// at lease a value is matched
if (option == 12 || option == 23 || option == 42)
{
   std::cout << "it's a good option\n";
}

// no value is matched
if (option != 12 && option != 23 && option != 42)
{
   std::cout << "it's a bad option\n";
}

This example has three comparison values for each case, but it could be 5, or 10, or any number. If it’s too many then perhaps a different approach should be taken. However, the question is, how do we express this in a simpler way in C++, rather than a long if condition?

C++ code samples before and after Ranges

The Ranges library proposal has been accepted for C++20 at the San Diego meeting of the standard committee in November last year. The library provides components for handling ranges of values aimed at simplifying our code. Unfortunately, the Ranges library is not very well documented, which makes it harder to grasp for those that want to learn it. This post is intended as an introduction based on examples of code written with and without Ranges.