anchor.diff:      let maxElement, set = extractMax set
       Set.foldBack reduction set maxElement
   
  -//
  +/// <summary>
  +/// Applies the given function to each element of the set.
  +/// Returns the set comprised of the results <c>x</c> for each element where the
  +/// function returns <c>Some(x)</c>.
  +/// </summary>
   [<CompiledName("Choose")>]
   let choose (chooser : 'T -> 'U option) (set : Set<'T>) : Set<'U> =
       // Preconditions
  
positive.code:         Set.toSeq set
          |> Seq.tryFind predicate
  
  //
  [<CompiledName("Find")>]
  let find (predicate : 'T -> bool) (set : Set<'T>) : 'T =
      // Preconditions
  
negative.code:         idx <- idx + 1
      state
  
  /// Applies a function to each element of the set, returning the results in an array.
  [<CompiledName("MapToArray")>]
  let mapToArray (mapping : 'T -> 'U) (set : Set<'T>) : 'U[] =
      // Preconditions
  