anchor.diff:                  toks
           pa_intro
       let DESTRUCT_TAC s = 
  -        let tac, rest = 
  -            (fix "Destruct pattern" parse_destruct << lex << explode) s
  +        let tac, rest = (fix "Destruct pattern" parse_destruct << lex << explode) s
           if rest = []
           then tac
  -        else failwith "Garbage after destruct pattern"
  +        else fun _ _ -> Choice.failwith "Garbage after destruct pattern"
       let INTRO_TAC s = 
  -        let tac, rest = 
  -            (fix "Introduction pattern" parse_intro << lex << explode) s
  +        let tac, rest = (fix "Introduction pattern" parse_intro << lex << explode) s
           if rest = []
           then tac
  -        else failwith "Garbage after intro pattern"
  +        else fun _ -> Choice.failwith "Garbage after intro pattern"
       let FIX_TAC s = 
           let tac, rest = (parse_fix << lex << explode) s
           if rest = []
           then tac
  -        else failwith "FIX_TAC: invalid pattern"
  +        else fun _ -> Choice.failwith "FIX_TAC: invalid pattern"
       DESTRUCT_TAC, FIX_TAC, INTRO_TAC
  
positive.code: (* ------------------------------------------------------------------------- *)
  (* More stuff about equality.                                                *)
  (* ------------------------------------------------------------------------- *)
  let EQ_REFL = 
      prove((parse_term @"!x:A. x = x"), 
            GEN_TAC
  
negative.code: 
  open FSharp.Compatibility.OCaml
  open FSharp.Compatibility.OCaml.Num
  
  open ExtCore.Control
  
  open NHol
  open lib
  