Control Flow in Clojure

Control flow operators

if

The structure of an if expression in clojure is as follows:

(if boolean-form then-form optional-else-form)

A boolean form evaluates to a truthy of falsey value. The then-form (first operand) is what the if exprssion returns if the boolean form returns as truthy. The else form is a optional second operand for if the boolean form returns falsey (nil).

do

Since the second operand in an if expression in Clojure will be evaluated automatically as an else statement (if falsey), to program multiple forms within your then or else operands you can wrap them in a do operator.

(if true (do (println "Success!") "By Zeus's hammer!") (do (println "Failure!") "By Aquarman's trident!"))

when

The when operator acts the same as the if operator except without the else argument. Because of this, when can be an alternative to using do to evaluate multiple forms, as long as you want the program to return nil if it returns a falsey value.

references

1. Higginbotham, Daniel. Clojure for the Brave and True Learn the Ultimate Language and Become a Better Programmer. Daniel Higginbotham, 2015, [https://www.braveclojure.com/clojure-for-the-brave-and-true/].