Functions: Basics

Code

(ns functions-basic.core)

(defn print-hello-world []
  (println "Hello world"))
(print-hello-world)
;; => nil

(defn get-hello [who]
  (str "Hello " who "!"))
(get-hello "world")
;; => "Hello world!"

(defn add [x y]
  (+ x y))
(add 1 2)
;; => 3

(defn print-hello [who]
  (println (get-hello who)))
(print-hello "world")
;; => nil

Explanation

Here is an explanation of the given Clojure code:

Here is a comprehensive explanation of the Clojure code:

1. Namespace definition: (ns functions-basic.core). This defines the namespace for the current file. ns stands for namespace, and functions-basic.core is the name of the namespace. A namespace is a container that allows you to group related functions and variables together, and it helps to avoid name clashes in large projects.
2. Function definition: (defn print-hello-world [] (println "Hello world")). This declares a function named print-hello-world with defn. The function takes no arguments, as indicated by the empty vector [], and prints the “Hello world” string to the console.
3. Function call: (print-hello-world). This is a call to the print-hello-world function. It will print “Hello world” to the console. The comment ;; => nil indicates that the function returns nil - Clojure functions by default return the value of their last statement, and the println function returns nil.
4. String concatenation function: (defn get-hello [who] (str "Hello " who "!")). This defines a function named get-hello that takes a single argument who and returns a string that starts with “Hello “, appends the value of who, and then adds “!” at the end. The str function is used to concatenate strings.
5. Function call with parameter: (get-hello "world"). This is a call to the get-hello function with the argument “world”. The function returns the string “Hello world!”.
6. Addition function: (defn add [x y] (+ x y)). This defines a function named add that takes two arguments x and y, and returns their sum. The + operator is used to add numbers in Clojure.
7. Function call with parameters: (add 1 2). This is a call to the add function with the arguments 1 and 2. The function returns the sum, which is 3.
8. Function definition with function call: (defn print-hello [who] (println (get-hello who))). This defines a function named print-hello that takes a single argument who. Inside this function, it first calls the get-hello function with the who argument and then prints the returned string.
9. Nested function call: (print-hello "world"). This is a call to the print-hello function with the argument “world”. This function calls the get-hello function with “world” as an argument, concatenates the return with “Hello " and “!”, then prints the result. Again, the comment ;; => nil shows the println function’s return value is nil.

This code provides examples of defining and calling functions in Clojure, including functions with no arguments, functions with arguments, and functions that call other functions. It also demonstrates string concatenation and addition.