OCaml Question: Write a function to sum all the ODD numbers between a & b (a is guaranteed to be smaller than b)

gistfile1.ml

let sumOdd a b =

  let rec inner a b = 
    if a>=b then b else a + (inner (a+2) b)

  in 

  let (new_a,new_b) = 
    (
      (if ((a mod 2) = 0) then (a+1) else a),
      (if ((b mod 2) = 0) then (b-1) else b)
    )
  
  in 
  
   inner new_a new_b;

Important lesson I learnt:

When writing a "let" there has to be an "in" following it. I ran into trouble when trying to set the new_a and new_b after checking if they were EVEN.