fibonacci.rb

def fibonacci(n, arr)
    a = 0
    b = 1
    n.times do
        temp = a
        # sets temp to be 0, 1 on the second loop
        a = b
        # sets b to be 1, still 1 on the second loop, 2 on the third loop
        b = temp + b
        arr << a
        # b = 0 + 1, gives you 1, same on the second loop, 1 + 1 on the third loop
    end
    return arr
end

p fibonacci(20, [])

n1 = 0
n2 = 1
arr = []

while arr.length < 20
    temp = n1
    # here we need a temporary variable to store the value of n1, this is because we have to reassign the variable n1 but we don't want to lose its value
    n1 = n2
    # here we get the value we need to push into our array
    arr << n1
    n2 = n2 + temp
    # here we add the value of temp with n2 to increment, remember that a fibonacci number is the previous two numbers in the cycle added togther 
end 
# here i'm using the fibonacci method in two different ways 
# one way uses times and one way uses a while loop and ends when the array is a certain length 
# nice way to see why we need to reassign sometimes