Question

Define a recursive function prefix that accepts a positive integer n and a list xs as input, and returns a list containing only the first n elements in xs. - This function must have a recursive definition and does not use any library functions!

Answer 1

Answer:

F# Code:

let rec prefix n list =

//Extracting head and tail elements

let valHead = (Listhead list)

let valTail = (Listtail list)

// Checking n value

match n with

| 0 -> []

| _ -> [valHead] at (prefix (n-1) valTail) // Creating list recursively

//Testing function

let lstT = [1; 2; 3; 4; 5]

printfn "%A" (prefix 3 lstT)

printfn "%A" (prefix 2 lstT)

printfn "%A" (prefix 4 lstT)

Step-by-step explanation: see attachment below for sample run