Question

F# ONLY SOMEONE SOLVED IN PYTHON JUST NOW. I NEED F SHARP PROGRAMMING THANKS

A more efficient version of the function for computing Tetranacci numbers can be defined by following three steps:

1. Implement a function which takes a list of integers and adds the sum of the top four elements to the head of the list (e.g., in F#, 1::1::1::1::[] should become 4::1::1::1::1::[]).
2. Implement a recursive function which accepts an integer n as input (again, assume n >= 0), and returns a list of integers from 0 to n in ascending order.
3. Implement a recursive function which computes the nth Tetranacci number in linear time. This function may use a linear amount of space to compute its result, but the number of recursive calls it makes must be linear in n.

Your task is to follow the three steps above, in order to implement the recursive function tetrn2 in F#.

• Hint: Try to define auxiliary functions first before taking on main function. You do not have to use auxiliary functions in your tetrn2, but they provide an insight on how to implement the tetrn2 function.

Answer 1

F# Code :

let tetr n =
let rec t a4 a3 a2 a1 = function //Recursive function
    | n when n = 0 -> a4 //Returns a4 if n = 0
    | n when n = 1 -> a3 //Returns a3 if n = 1
    | n when n = 2 -> a2 //Returns a2 if n = 2
    | n when n = 3 -> a1 //Returns a1 if n = 3
    | n -> t a3 a2 a1 (a1 + a2 + a3 + a4) (n - 1) //Returns list appended with sum of last four number in the front of the list, if n > 3 (Its a recursive call)
t 0 1 1 2 n

ScreenShot of Code :

1 2 3 4 5 6 let tetr n = let rec t a4 a3 a2 a1 = function //Recursive function I n when n = 0 -> a4 //Returns a4 if n = 0 In when n = 1 -> a3 //Returns a3 if n = 1 In when n = 2 -> a2 //Returns a2 if n = 2 | n when n = 3 -> a1 //Returns al if n = 3 In -> t a3 a2 a1 (a1 + a2 + a3 + a4) (n - 1) //Returns list appended with sum of last four number in the front of the list, if n > 3 (I to 1 1 2 7 8

(I have included comments to explain the code)