Eureka! The Ultimate Beginner’s Guide to Understanding Functions in Programming
Tags: programming, function, javascript, python
Published: 2023-01-02 09:37:48

In programming, a `function` is a piece of code that performs a specific task. It's like a recipe in a cookbook - it tells you how to do something.

Every `function` has an `input` and an `output`. The `input` to a `function` is the information that it needs to do its job. This information is passed to the `function` when it is called.

The `output` of a function is the result of the task that it performs. When the `function` is finished running, it produces an `output`, which is usually a value of some kind.

For example, consider a function that calculates the _area of a rectangle_. The `input` to this `function` would be the `width` and `height` of the rectangle. The `output` would be the `area` of the rectangle.

Here's an example of how a `function` might be defined in code:

**Python:**

```
def calculate_area(width, height):
  area = width * height
  return area
```

**JavaScript:**

```
function calculate_area(width, height){
 let  area = width * height;
  return area;
}
```
In this example, the `function` is called `calculate_area`, and it takes `two input` values: `width` and `height`. When the `function `is called, it calculates the `area `of the rectangle by multiplying the `width `and `height `together. The result is returned as the `output `of the `function`.

**Did I confuse you? 😕**

okay! Let me explain again...

In a `function` definition, the names that you give to the `input` values are called `parameters`. For example, in the function definition `def calculate_area(width, height):`, `width `and `height `are the `parameters`.

When you call a `function`, you pass it some values, which are called `arguments`. For example, if you call the `calculate_area` function like this:

```
area = calculate_area(5, 10)
```
In this case, the values `5` and `10` are the `arguments`. They are the `input `to the `function`, and they are passed to the function in place of the `parameters` `width `and `height`.

**So to summarize:**

`Parameters `are the names that you give to the `input` values in a function definition.

`Arguments` are the actual `values` that are passed to a `function `when it is called.

**Still confused! 😕 Don't worry! Let's take a real-life example of a machine.**

Imagine a machine that makes lemonade🍹. This machine has a specific task: it takes some ingredients (water💧, sugar🥄, and lemons🍋) and produces a finished product (lemonade🍹).

The `input` to the machine is the ingredients (water, sugar, and lemons). These are like the `arguments` that are passed to a function when it is called.

The `output` of the machine is the lemonade. This is like the `return` value of a function.

The machine has a set of instructions that tell it how to make the lemonade. These instructions are like the **code inside a function**. The instructions tell the machine what to do with the ingredients to produce the final product.

The machine also has a set of `buttons` and `controls` that you can use to operate it. These controls are like the `parameters` of a `function`. They are the names that you give to the `input` values in the `function` definition.

I hope this analogy helps to make functions in programming more concrete!

**That's great!👍 Yes, I understand.😄 What if a machine malfunctions or a function does not return anything?**

In programming, if a `function` doesn't return a value, it is said to `return None`.

None is a special value in Python that represents the absence of a value or a `null` value. It is an `object` of its own data type, called `NoneType`.

If a `function` is supposed to `return` a value but doesn't, it will implicitly `return None`. For example, consider the following function:

**Python:**

```
def calculate_area(width, height):
  area = width * height
```
This `function` calculates the `area` of a `rectangle`, but it doesn't have a `return` statement. As a result, it will implicitly `return None`.

Here's an example of how you might call this function and print the result:

```
area = calculate_area(5, 10)
print(area)  # prints "None"
```
On the other hand, if a `function` is not supposed to `return` a value, you can use the `void return` type to indicate this. In Python, you can use the `pass` statement to create a function with a `void return` type. For example:

```
def print_hello():
  print("Hello!")
  pass
```

This `function` doesn't `return` a value, so it has a `void return` type. When you call it, it will simply `print` the message "Hello!" but not `return` anything.

I hope this helps you to understand!

**Okay! Let's have a real-life example**

Here's an analogy for the `None value` in Python:

Imagine a vending `machine` that dispenses snacks. Sometimes, the vending machine might be out of a particular snack that you want. In this case, the vending machine wouldn't be able to give you the snack that you requested.

In this situation, you could say that the vending machine "**returned**" None. It didn't return a snack (which would be the expected output), but rather it returned the absence of a snack.

In a similar way, a `function` in Python that returns None is indicating that it didn't produce an output value. It didn't return a specific result, but rather it returned the absence of a result.

I hope this analogy helps to make the concept of None more concrete! 

In summary, I hope you now have a better understanding of what a `function` is and how it works. Keep coding. 👨‍💻