CODEWITHSUNDEEP
f#sequencefibonacci
Marc Karam
Marc Karam

Reputation: 463

How do I print out the entire Fibonacci sequence up to a user inputted value in F#?

So I have a program that, currently, finds the fibonacci equivalent of a user inputted value, e.g. 6 would be 5 (or 13 depending on whether or not you start with a 0). Personally I prefer the sequence starting with 0.

    open System

    let rec fib (n1 : bigint)  (n2 : bigint) c =
        if c = 1 then
            n2
        else
            fib n2 (n1+n2) (c-1);;

    let GetFib n =
        (fib 1I 1I n);;

    let input = Console.ReadLine()
    Console.WriteLine(GetFib (Int32.Parse input))

The problem is that ALL it does is find the equivalent number in the sequence. I am trying to get it to print out all the values up to that user inputted value, e.g. 6 would print out 0,1,1,2,3,5. If anyone could help me figure out how to print out the whole sequence, that would be very helpful. Also if anyone can look at my code and tell me how to make it start at 0 when printing out the whole sequence, that would also be very much appreciated.

Thank you in advance for any help.

Upvotes: 3

Views: 172

Answers (1)

Pash101
Pash101

Reputation: 641

Take a look at the link s952163 gave you in the comments - that shows ways of generating a fibonnaci sequence using Seq expressions and also explains why these are useful.

The following will print a sequence up until the specified sequence number:

let fibsTo n = Seq.unfold (fun (m,n) -> Some (m, (n,n+m))) (0I,1I)  
              |>Seq.takeWhile (fun x -> x <= n)

let input = Console.ReadLine()

(fibsTo  (Numerics.BigInteger.Parse input))|>Seq.iter(printfn "%A")

Note the use of printfn rather than console.writeline, the former is more idiomatic.

Also, you may want to consider handling negative inputs here as these will throw an error.

Upvotes: 2

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