F#: Mutually recursive functions [duplicate]

Question

Possible Duplicate:
[F#] How to have two methods calling each other?

Hello all,

I Have a scenario where I have two functions that would benefit from being mutually recursive but I'm not really sure how to do this in F#

My scenario is not as simple as the following code, but I'd like to get something similar to compile:

let rec f x =
  if x>0 then
    g (x-1)
  else
    x

let rec g x =
  if x>0 then
    f (x-1)
  else
    x

Theall

See also https://mcmap.net/q/430846/-f-forward-type-declarations – Tusk

I hesitate to mark this one as the duplicate, because the title is probably better... – Jimmyjimsonweed

@Benjol: Generally we don not delete duplicates with substantially different titles in order to improve searchability, but we still close them. – Phototype

Answer 1

You can also use let rec ... and form:

let rec f x =
  if x>0 then
    g (x-1)
  else
    x

and g x =
  if x>0 then
    f (x-1)
  else
    x

Brynne

Beat me to it by 42 seconds... :-) – Israel

+1, Nice, didn't realize you could use and with let bindings. I thought it's usage was restricted to type declarations. – Padlock

It's specially useful (necessary) if you have mutually recursive types (like two DUs) and two functions that take each as an input argument. – Brynne

Answer 2

To get mutually recursive functions simply pass one to the other as a parameter

let rec f g x =
  if x>0 then
    g (x-1)
  else
    x

let rec g x =
  if x>0 then
    f g (x-1)
  else
    x

Padlock

Answer 3

Use the let rec ... and ... construct:

let rec f x =
  if x>0 then
    g (x-1)
  else
    x

and g x =
  if x>0 then
    f (x-1)
  else
    x

Israel