anchor.diff:  (* ------------------------------------------------------------------------- *)
   
   /// Read file and convert content into a list of strings.
  +// OPTIMIZE : Use a StreamReader here instead of the OCaml-compatibility stuff.
   let strings_of_file filename = 
       let fd = 
  -        try 
  +        try
               Pervasives.open_in filename
           with
  -        | Sys_error _ -> failwith("strings_of_file: can't open " + filename)
  +        | Sys_error _ ->
  +            failwith("strings_of_file: can't open " + filename)
       let rec suck_lines acc = 
           try 
               let l = Pervasives.input_line fd
  
positive.code: (* ------------------------------------------------------------------------- *)
  
  /// Concatenates a list of strings into one string.
  // OPTIMIZE : Make this an alias for List.sortWith.
  let implode l = itlist (+) l ""
  
  /// Converts a string into a list of single-character strings.
  
negative.code:     | Microsoft.FSharp.Core.Operators.Failure s -> Some s
      | _ -> None
  
  module Ratio =
      open System.Diagnostics
      open FSharp.Compatibility.OCaml
      open FSharp.Compatibility.OCaml.Num
  
      let inline numerator_ratio(r : Ratio.ratio) = r.Numerator
      let inline denominator_ratio(r : Ratio.ratio) = r.Denominator
  
      //
      let [<Literal>] private normalize_ratio_warning =
          "Ratio.normalize_ratio does not actually normalize the value \
           (the functionality has not yet been implemented), so other functions \
           which rely on that invariant will not work properly."
  
      // NOTE : not sure what kind of normalization should be done here
      // TODO : Implement this function correctly in the next version of
      // FSharp.Compatibility.OCaml, then upgrade to that version ASAP.
      [<Experimental(normalize_ratio_warning)>]
      let normalize_ratio x =
          Debug.Write "Warning: "
          Debug.WriteLine normalize_ratio_warning
          x
  
  
  (* ------------------------------------------------------------------------- *)
  (* Combinators.                                                              *)
  