Lesson 7. Complex nested expressions
At this point, your mind starts to get used to the wrapping parenthesis in Clojure: simple compound expressions like (+ 2 3), (* 3 4 5) and (or true false) don’t feel as weird as they felt when you start to read this book.
But what about complex nested expressions like (or (and (> 3 2) (zero? 2)) (not (= 2 3)))? It probably still makes you a bit of discomfort. That’s perfectly fine. The purpose of this Lesson that concludes Unit 1 is to make you feel more comfortable with complex nested expressions.
After reading this lesson, you will be able to:
- Visualize a complex nested expression in a tree diagram
- Describe the structure of a complex nested expression
7.1 Visualization
Now that our logical operations portfolio is complete, we can write some complex boolean expressions. Once you understand the mechanics of the evaluation of a complex boolean expression, you will be able to understand the mechanics of the evaluation of any Clojure expression.
Let’s inspect a nested expression that combines and, or and not.
(or (and (> 3 2) (zero? 2)) (not (= 2 3)))
This expression looks a bit scary. Let’s reformat it, by having each form argument in a separate line:
(or (and (> 3 2)
(zero? 2))
(not (= 2 3)))
When you develop in a Clojure environment, the auto formatting (also called smart indentation) is done by the editor. In Unit 2, we will see how the REPL handles auto formatting.