Learn the syntax, data types, and operations essential for programming in Scala

Become a Scala Developer

In this module, we will learn Scala from the ground up. This module aims to teach us how to write basic programs, assuming we have no prior knowledge of the language. We will start with a brief introduction to Scala to understand its functionality and applications. We will then move discuss the key features and functions of the language (data types, functions, classes, etc.) in detail. In the end, we will have all the basic knowledge of how to program in Scala.

Learn Scala from Scratch

## Task

In this challenge, you had to create a tail-recursive factorial function.


## Solution

A skeleton of the function was already provided for you. Let's look it over.

```
def factorial(x: Int): Int = {
  def loop(accumulator: Int, x: Int): Int = {
    

  }
  loop(1,x)
}
```

As before, `factorial` takes a single parameter `x` of type `Int`. However, this time, its function body consists of a nested function `loop`. `loop` is the tail recursive part of `factorial`. It has two parameters `accumulator` and `x`. The accumulator stores the current value of the factorial in each recursive call. This is why when we pass **1** as the initial accumulator when `loop` is called in the function body of factorial.

```
loop(1,x)
```

**1** is the smallest possible factorial.

Hence, if the number whose factorial we want to find is **0**, we will simply return the accumulator as is, this is our base case.

```
if(x == 0) accumulator
```
The recursive case is if `x` is not equal to **0**. We will recursively call loop in this case. The new `accumulator` to be passed will be `accumulator * x` and the new `x` to be passed will be `x-1`.

```
else loop(accumulator*x,x-1)
```
As the last thing being done by `loop` is a recursive call, it is a tail-recursive function. 

You can find the complete solution below:

>You were required to write the code on **line 3** and **line 4**.

# Task

In this challenge, you had to create a tail-recursive factorial function.


# Solution

A skeleton of the function was already provided for you. Let's look it over.

```
def factorial(x: Int): Int = {
  def loop(accumulator: Int, x: Int): Int = {
    

  }
  loop(1,x)
}
```

As before, `factorial` takes a single parameter `x` of type `Int`. However, this time, its function body consists of a nested function `loop`. `loop` is the tail recursive part of `factorial`. It has two parameters `accumulator` and `x`. The accumulator stores the current value of the factorial in each recursive call. This is why when we pass **1** as the initial accumulator when `loop` is called in the function body of factorial.

```
loop(1,x)
```

**1** is the smallest possible factorial.

Hence, if the number whose factorial we want to find is **0**, we will simply return the accumulator as is, this is our base case.

```
if(x == 0) accumulator
```
The recursive case is if `x` is not equal to **0**. We will recursively call loop in this case. The new `accumulator` to be passed will be `accumulator * x` and the new `x` to be passed will be `x-1`.

```
else loop(accumulator*x,x-1)
```
As the last thing being done by `loop` is a recursive call, it is a tail-recursive function. 

You can find the complete solution below:

>You were required to write the code on **line 3** and **line 4**.

In the following lesson, we will go over the solution of the challenge:  Tail Recursion.

Getting to Know Scala

Variables and Types

Operating with Operators

Strings and How to Use Them

Scala's Collection Library

Control Structures

Getting Started with Functions

Higher-Order Functions

Classes and Objects

Conclusion

Solution Review: Tail Recursion

Task

Solution