So, basically, now I'm studying a theoretical course about the fundamental concepts of Functional Programming. In a few next days, I'll be sharing this knowledge with you. First things first, and the first thing today is 'First-Class Citizen.' T his is a characteristic of objects. This concept applies to functions (yes, functions are indeed objects). But what the heck are First-Class Citizen functions? This means that such a function can: - Be assigned to a variable - Be passed as an argument to some other function - Be returned as a return value from another function - Be stored in data structures, such as a list, array, etc. Freaking awesome, isn't it? 🤨 First-Class Citizen functions can be very handy in capable hands. Just imagine how beautiful and reusable, yet completely incomprehensible and ugly your code could become with them (If hands are not capable) 🤣 A pretty simple example of such a function: