fibonacci_progression.rb

def fibs(n)
    fib = [0, 1]
    while fib.length < n
        fib << fib[-1] + fib[-2]
    end
    fib.slice(0, n)
end

def fibs_rec(n)
    return [0,1].slice(0, n) if n <= 2
    a = fibs_rec(n-1)
    a << a[-1] + a[-2]
end

def fibs_single(n)
    return n <= 2 ? [0, 1].slice(0,n) : fibs_single(n-1) << fibs_single(n-1)[-1] + fibs_single(n-1)[-2]
end

def time_measure

    fibs_start = Time.now.to_f
    fibs(10)
    fibs_end = Time.now.to_f
    puts fibs_end - fibs_start

    fibs_rec_start = Time.now.to_f
    fibs_rec(10)
    fibs_rec_end = Time.now.to_f
    puts fibs_rec_end - fibs_rec_start 

    fibs_single_start = Time.now.to_f
    fibs_single(10)
    fibs_single_end = Time.now.to_f
    puts fibs_single_end - fibs_single_start 

end

p fibs(8) # => 
p fibs_rec(8) # =>
p fibs_single(8) # =>

time_measure