Question

I begin a “new” Fibonacci algorithm, but it’s not working. It’s very simple:

    --fiblista 0 n = [0]
    --fiblista 1 n = [1]
    fiblista a n 
        | a <= n = (0:1:tail, ((fiblista!!d)+(fiblista!!c))) fiblista a+1 n 
        where d = a - 1 
              c = a - 2

Example:

First error code: parse error on input `=’

Any idea how to fix this algorithm?
I read thousand of example Fibonacci algorithm in haskell, but I need to write a new one.

Answer 1

Your indentation is wrong. Try:

fiblista 0 n = [0]
fiblista 1 n = [1]
fiblista a n 
    | a < n = (tail, ((fiblista!!d)+(fiblista!!c))) fiblista a+1 n 
  where d = a - 1 
        c = a - 2

But this code still won’t compile. fiblista is a function with two parameters, but you also try to use it as a list. You also try to use a tuple as a function.

If you are still stuck writing your function, it would help if you could describe what the parameters to fiblista are, and what it should return. Include a type signature.

Is this homework?

---

So.

fiblista a n is a list of Fibonacci numbers, starting with the a^th Fibonacci number, and ending with the (n-1)^th Fibonacci number.

This is a list question.

Imagine you had a list of all the Fibonacci numbers. (This would be the same as fiblista 0 ∞, if ∞ was a valid Haskell value.) You would then be able to use the standard list functions take and drop to calculate fiblista a n.