# RFC for Table of Constants TZIP

**URL:** https://forum.tezosagora.org/t/rfc-for-table-of-constants-tzip/2579
**Category:** TZIP
**Created:** [January 5, 2021, 3:43am UTC](https://forum.tezosagora.org/t/rfc-for-table-of-constants-tzip/2579 "2021-01-05T03:43:17Z")
**Posts on this page:** 1
**Showing post:** 11

<div class="post-metadata">

### Author: ![tom](https://forum.tezosagora.org/letter_avatar_proxy/v4/letter/t/3d9bf3/32.png) [@tom](https://forum.tezosagora.org/u/tom)
#### Post date: [March 17, 2021, 6:42pm UTC](https://forum.tezosagora.org/t/rfc-for-table-of-constants-tzip/2579/11 "2021-03-17T18:42:13Z")

</div>

Another problem with hashes for addresses is that protocol migrations might rewrite the code (e.g. when some instruction is deprecated) and then either the hash needs to be rewritten too, or it will no longer actually be the hash of the value.

It seems OK to me to guarantee that the address is either the hash of the value, _or_ the hash of an old version of the value when the value was rewritten by a protocol migration…

---

_[View the full topic](https://forum.tezosagora.org/t/rfc-for-table-of-constants-tzip/2579)._