anchor.diff:          // Return the picked value, if any.
           picked
   
  -    //
  +    /// <summary>
  +    /// Applies the given function to successive characters, returning the first result where the function
  +    /// returns <c>Some(x)</c>. If the function never returns <c>Some(x)</c>, <c>KeyNotFoundException</c> is raised.
  +    /// </summary>
  +    /// <param name="picker"></param>
  +    /// <param name="substr"></param>
  +    /// <returns></returns>
       [<CompiledName("Pick")>]
       let pick (picker : char -> 'T option) (substr : substring) : 'T =
           // Preconditions
  
positive.code:             Some (index - 1)
          else None
  
      /// Returns the index of the first character in the substring which satisfies the given predicate.
      [<CompiledName("FindIndex")>]
      let findIndex (predicate : char -> bool) (substr : substring) : int =
          // Preconditions
  
negative.code:                 raise <| System.Collections.Generic.KeyNotFoundException ()
              | idx -> idx
  
      /// <summary>Returns the index of the last occurrence of a specified character within a substring.</summary>
      /// <param name="c"></param>
      /// <param name="substr"></param>
      /// <returns></returns>
      [<CompiledName("TryFindIndexOfBack")>]
      let tryFindIndexOfBack (c : char) (substr : substring) =
          // Preconditions
  