F#

let square x = x * x
let isOdd x = x % 2 <> 0

let sumOfOddSquares nums =
    nums
    |> List.filter isOdd
    |> List.sumBy square

let numbers = [1; 2; 3; 4; 5]
let sum = sumOfOddSquares numbers

printfn "The sum of the odd squares in %A is %d" numbers sum

type Shape =
    | Square of side: double
    | Rectangle of width: double * length: double

let getArea shape =
    match shape with
    | Square side -> side * side
    | Rectangle (width, length) -> width * length

let square = Square 2.0
printfn $"The area of the square is {getArea square}"
                                   

type Customer(firstName, middleInitial, lastName) = 
    member this.FirstName = firstName
    member this.MiddleInitial = middleInitial
    member this.LastName = lastName

    member this.SayFullName() =
        $"{this.FirstName} {this.MiddleInitial} {this.LastName}"

let customer = Customer("Emillia", "C", "Miller")

printfn $"Hello, I'm {customer.SayFullName()}!"