anchor.diff:              //keyNotFound ""
               raise <| System.Collections.Generic.KeyNotFoundException ()
   
  -    /// Returns the first character in the substring which satisfies the given predicate.
  +    /// <summary>Returns the first character in the substring which satisfies the given predicate.</summary>
  +    /// <param name="predicate"></param>
  +    /// <param name="substr"></param>
  +    /// <returns></returns>
       [<CompiledName("TryFind")>]
       let tryFind (predicate : char -> bool) (substr : substring) : char option =
           // Preconditions
  
positive.code:                 state <- folder.Invoke (state, substringIndex, subUnsafe substr offset length)
              state
  
          /// Applies the given function to each of the substrings in the input string that are
          /// delimited by elements of a specified Unicode character array, threading an accumulator
          /// argument through the computation. The integer index
          /// applied to the function is the index of the substring within the virtual array of
          /// substrings in the input string. For example, if the newline character (\n) is used
          /// as the separator, the index of each substring would be the line number.
          [<CompiledName("FoldIndexed")>]
          let foldi (separator : char[]) (folder : 'State -> int -> substring -> 'State) (state : 'State) (substr : substring) : 'State =
              // Preconditions
  
negative.code:             // Return the specified character from the underlying string.
              this.String.[this.Offset + index]
  
      /// <summary>Determines whether the beginning of this substring value matches the specified string.</summary>
      /// <param name="value">The string to compare.</param>
      /// <returns></returns>
      member this.StartsWith (value : string) : bool =
          // Preconditions
          checkNonNull "value" value
  