# Problem statement

If there's a number `n`, find the factorial of `n`.

Example 1:
- Input: `n`=`5`
- Output: `120`

Example 2:
- Input: `n`=`7`
- Output: `5040`

## Solution 1: Recursion

In this solution, we use the following recursive expression to calculate the factorial of `n`:

```
fact(n) = n * fact(n-1)
```
The code implementation is as follows:

fact n = if n == 0 then 1 else n * fact(n-1)
main = print (fact 5)

## Explanation

- Line 1: We define a function, `fact`, that takes `n` and recursively calculates the factorial of `n`.
- Line 2: We invoke the `fact` function with `5` as the argument.

## Solution 2: The `product` function

The **`product` function** in Haskell multiplies all the elements in a given list.

The steps are as follows:

- Generate the list of numbers from `1` to `n`. 
- Use the `product` function to multiply all the numbers in the list.

## Code

-- Generating the list of numbers from 1 to n
-- and calling the product function to multiply all the numbers in the list.
fact n = product [1..n] 
main = print (fact 5)

How to find the factorial of a number in Haskell

Recursively using fact(n) = n * fact(n-1) or by multiplying a list from 1 to n.

How to find the factorial of a number in Haskell

Problem statement

Solution 1: Recursion

Explanation

Solution 2: The product function

Code

Solution 2: The `product` function