Exercise - Functions - Training

3 minutes

In this exercise, you make your code reusable. It's code that another programmer on your team wrote, but your job is to turn it into functions.

Create functions

Start by scaffolding a new F# project, and then take a piece of code and turn that into a function with parameters.

Create a new F# project by running dotnet new.

dotnet new console --language F# -o Functions
cd Functions

Now that you have a new project, let's look at the code.

Here's the code from your colleague.

let no = card % 13
if no = 1 then "Ace"
elif no = 0 then "King"
elif no = 12 then "Queen"
elif no = 11 then "Jack"
else string no

Replace the default code in the Program.fs file with the following code:
```
let cardFace card = 
   let no = card % 13
   if no = 1 then "Ace"
   elif no = 0 then "King"
   elif no = 12 then "Queen"
   elif no = 11 then "Jack"
   else string no
```
The first line of this code let cardFace card makes it into a function. It's now a function called cardface() that takes the parameter card.
Add the following code below the cardface() function.
```
printfn "%s" (cardFace 11)
```
Run the project by calling dotnet run in the console.
```
dotnet run
```
You now see the following output:
```
Jack
```

Congratulations! You've taken a piece of code that you wanted to make reusable and turned it into a function.

Add types

You've turned your colleague's code into a function. To make this code more readable, you decide to add type definitions to it.

Modify your existing cardface() function to look like so:

let cardFace (card:int) = 
    let no = card % 13
    if no = 1 then "Ace"
    elif no = 0 then "King"
    elif no = 12 then "Queen"
    elif no = 11 then "Jack"
    else string no

Now run the project dotnet run.
```
dotnet run
```
You now see the following output:
```
Jack
```
The code still works and you've made it clearer by adding a type to the input parameter.

Alter your cardface() function to look like so:

let cardFace (card:int) :string = 
    let no = card % 13
    if no = 14 || no = 1 then "Ace"
    elif no = 13 then "King"
    elif no = 12 then "Queen"
    elif no = 11 then "Jack"
    else string no

At this point, you've added a return type to the function :string, means the function returns a string.

Run the project dotnet run.
```
dotnet run
```
Once again, you should see the following output:
```
Jack
```

Congratulations! Your code now has types added to it.

Continue

Exercise - Functions

Create functions

Add types

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