anchor.diff:        elif typ = typeof<byte> then box 1uy
         elif typ = typeof<sbyte> then box 1y
         elif typ = typeof<bigint> then box 1I
  -      elif typ = typeof<bignum> then box 1N
         elif typ = typeof<nativeint> then box 1n
         elif typ = typeof<unativeint> then box 1un
         else invalidArg "typ" ("unsupported " + (string typ))
  
positive.code:       || typ = typeof<byte>
        || typ = typeof<sbyte>
        || typ = typeof<bigint>
        || typ = typeof<bignum>
        || typ = typeof<nativeint>
        || typ = typeof<unativeint>
  
  
negative.code:       elif typ = typeof<byte> then box 0uy
        elif typ = typeof<sbyte> then box 0y
        elif typ = typeof<bigint> then box 0I
        elif typ = typeof<nativeint> then box 0n
        elif typ = typeof<unativeint> then box 0un
        else invalidArg "typ" ("unsupported " + (string typ))
  