Fortran Procedures - Functions and Subroutines Recursive Procedures
Example
In Fortran functions and subroutines need to be explicitly declared as recursive, if they are to call themselves again, directly or indirectly. Thus, a recursive implementation of the Fibonacci series could look like this:
recursive function fibonacci(term) result(fibo)
integer, intent(in) :: term
integer :: fibo
if (term <= 1) then
fibo = 1
else
fibo = fibonacci(term-1) + fibonacci(term-2)
end if
end function fibonacci
Another example is allowed to calculate factorial:
recursive function factorial(n) result(f)
integer :: f
integer, intent(in) :: n
if(n == 0) then
f = 1
else
f = n * f(n-1)
end if
end function factorial
For a function to directly recursively reference itself its definition must use the result suffix.
It is not possible for a function to be both recursive and elemental.
