When to use “if” and “when” in Clojure?

Question

When is one better than the other? Is one faster than the other or does the only difference is the return of false or nil?

Answer 1

Use if when you have two different expressions: for true clause and for false clause.

when and when-not are useful in two cases:

• when you want to perform one or several (implicit do helps here) non-pure operations conditionally;
• when you want to evaluate something when some predicate evaluates to true (or false in case of when-not), and return nil in opposite case.

---

only difference is the return of false or nil

There is no major difference between false and nil, as the both evaluate to false in logical context.