anchor.diff:  let num_10 = Int 10
   
   let pow2 (n:int) = 
  -    if n < 0 
  -        then 
  -            let n' = System.Math.Abs(n)
  -            (Int 1) / (power_num num_2 (Int n'))
  -        else power_num num_2 (Int n)
  -
  -let pow10 (n:int) = 
  -    if n < 0 
  -        then 
  -            let n' = System.Math.Abs(n)
  -            (Int 1) / (power_num num_10 (Int n'))
  -        else power_num num_10 (Int n)
  +    if n < 0 then
  +        let n' = System.Math.Abs(n)
  +        (Int 1) / (power_num num_2 (Int n'))
  +    else power_num num_2 (Int n)
  +
  +let pow10 (n:int) =
  +    if n < 0 then 
  +        let n' = System.Math.Abs(n)
  +        (Int 1) / (power_num num_10 (Int n'))
  +    else power_num num_10 (Int n)
   
   /// Returns numerator and denominator of normalized fraction.
   let numdom r =
  
positive.code:     | [] -> failwith "last"
  
  /// Computes the sub-list of a list consisting of all but the last element.
  // OPTIMIZE : Make this an alias for List.dropLast.
  let rec butlast l = 
      match l with
      | [_] -> []
  
negative.code: (* ------------------------------------------------------------------------- *)
  
  /// Iterates a function a fixed number of times.
  [<Obsolete("Use Choice.funpow instead.")>]
  let rec funpow n f x = 
      if n < 1 then x
      else funpow (n - 1) f (f x)
  