Function in Python, Javascript and R

A function is what make a code reusable, you write a piece of code once and you use it as many times as you want. These function can either be built-in or custom constructed (user-defined) functions.

Programming languages (Python, Javascript and R in this case) have built in functions. These are functions that are already available by default within the language engine for you to use. There are many of these built-in functions, just to give an example of one lets look at a function that calculates the square root of a number.

Built-in square root function in Python

In python, this function is available in the built-in math module.

import math 
print(math.sqrt(25))

User-defined/Constructed square root function in Python

def sqrt_num(x):
    num_sqrt = x ** 0.5
    print(num_sqrt)

sqrt_num(25)

Built-in square root function in JavaScript

In JavaScript, this function is available in the built-in math library.

Math.sqrt(25);

User-defined/Constructed square root function in JavaScript

function sqrt_num(x){
    return num_sqrt = x ** 0.5;
}

Built-in square root function in R

In R, this function is directly available as seen below.

sqrt(25)

User-defined/Constructed square root function in R

sqrt_num <- function (x){
    num_sqrt = x ** 0.5
    print(num_sqrt)
}

That is it!