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Merge pull request #263 from urbit/nock-10

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Add Nock 10 explanation
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Sigilante 2023-01-09 08:18:23 -06:00 committed by GitHub
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content/reference/nock/explanation.md
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@ -522,6 +522,24 @@ With `c`, we produce a noun which contains both code and data - a
**core**. We use this core as the subject, and evaluate the
formula within it at slot `b`.
### `10`, replace at address
`10` is how Nock updates a tree by altering a particular slot.
```
*[a 10 [b c] d] #[b *[a c] *[a d]]
```
This operation relies on the `#` hax operator, which has the form
```
#[mem-slot new-val target-tree]
```
This replaces the memory slot `mem-slot` in `target-tree` with `new-val`.
So all together, `10` means that we calculate `*[a c]` and `*[a d]`, then replace memory slot `b` in the latter with the result of the former.
### `6`, if-then-else
This looks much scarier than it is: