These qualities make it easier for you to reason about your programs because the functions are completely isolated, unable to impact other parts of your system. That is, the function can’t make any changes that are observable outside the function itself-for example, by changing an externally accessible mutable object or writing to a file. This is called referential transparency, and you can add it to your list of $5 programming terms. It always returns the same result if given the same arguments.

What makes them pure functions, and why does it matter? A function is pure if it meets two qualifications: Once you shove all this knowledge into your brain matter, you’ll have an entirely new approach to problem solving!Īfter going over these topics, you’ll put everything you’ve learned to use by writing a terminal-based game inspired by an ancient, mystic mind- training device found in Cracker Barrel restaurants across America: Peg Thing ! Pure Functions: What and WhyĮxcept for println and rand, all the functions you’ve used up till now have been pure functions. The core concepts you’ll learn include: what pure functions are and why they’re useful how to work with immutable data structures and why they’re superior to their mutable cousins how disentangling data and functions gives you more power and flexibility and why it’s powerful to program to a small set of data abstractions. You’ll begin integrating your experience into a new functional programming mindset. In this chapter, you’ll learn how to think about your programming tasks in a way that makes the best use of those tools. So far, you’ve focused on becoming familiar with the tools that Clojure provides: immutable data structures, functions, abstractions, and so on.

Another word for brave and confident