anchor.diff:  
   let NSUM_PAIR = 
       prove
  -        ((parse_term 
  -              "!f m n. nsum(2*m..2*n+1) f = nsum(m..n) (\i. f(2*i) + f(2*i+1))"), 
  +        ((parse_term @"!f m n. nsum(2*m..2*n+1) f = nsum(m..n) (\i. f(2*i) + f(2*i+1))"), 
            MP_TAC(MATCH_MP ITERATE_PAIR MONOIDAL_ADD)
            |> THEN <| REWRITE_TAC [nsum; NEUTRAL_ADD])
   
  
positive.code: 
  let NSUM_POS_BOUND = 
      prove
          ((parse_term 
                "!f b s. FINITE s /\ nsum s f <= b ==> !x:A. x IN s ==> f x <= b"), 
           GEN_TAC
           |> THEN <| GEN_TAC
           |> THEN <| REWRITE_TAC [IMP_CONJ]
  
negative.code: 
  let FINITE_SUPPORT_DELTA = 
      prove
          ((parse_term @"!op f a. FINITE(support op (\x. if x = a then f(x) else neutral op) s)"), 
           REWRITE_TAC [SUPPORT_DELTA]
           |> THEN <| REPEAT GEN_TAC
           |> THEN <| COND_CASES_TAC
  