[jessaustin]

TFA would seem more reliable if it didn't have such a needlessly obscurantist Fortran-python code comparison. Nothing about the two languages calls for different base case logic! That is, in order to prevent confusion, the "Python3" code should have been this:

  def fibonacci(n):
    if n < 2:
      return n
    else:
      return fibonacci(n-1) + fibonacci(n-2)

[hyperrail]

From the other side, I thought the Fortran code had too much syntactic ceremony.

I haven't written Fortran in a while, but I was pretty sure that for illustrative examples like this, you could dispense with the entire MODULE declaration, the use of END FUNCTION Fibonacci instead of just END, and the usually-optional :: separator between the variable's type and name.

Something like this? Again, no recent experience:

  implicit none

  recursive function fibonacci(n) result (fib)
    integer n
    integer fib
    if (n < 2) then
      fib = n
    else
      fib = fibonacci(n - 1) + fibonacci(n - 2)
    endif
  end

(The IMPLICIT NONE has to stay because of the now-regrettable Fortran convention that without it, the type of a variable is determined by the first character of the name (n would be integer because variables starting with m, n, i, etc. are integer, while fib would be floating point).)