Immutable Local Bindings

Names can be bound to values & and data structures with either the def or let function. The def binding is global to the namespace, however the let function is local to its use.

Hint The let function is typically used to define names within a function definition, or in snippets of code created during repl driven development.

(let [five 5]
  (str "Within the let expression the value is " five))
;; => Within the let expression the value is 5

;; evaluating the name five outside the let expression returns an error
five
;; => Unable to resolve symbol: five in this context

Note Create a local binding called number that represents the value 5 using the let function. Increment the number, then print out the value of number.

(let [number 5]
   (inc number)
   (str "The number is still " number))

So the value that any local binding points to is immutable too.