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Improve readability of SSZ type defaults

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Matt Garnett 2019-08-08 09:59:06 -04:00 committed by protolambda
parent 3e45bf4a67
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1 changed files with 12 additions and 2 deletions
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specs/simple-serialize.md
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@ -62,7 +62,7 @@
* **bitlist**: ordered variable-length collection of `boolean` values, limited to `N` bits
* notation `Bitlist[N]`
* **union**: union type containing one of the given subtypes
* notation `Union[type_1, type_2, ...]`, e.g. `union[null, uint64]`
* notation `Union[type_0, type_1, ...]`, e.g. `union[null, uint64]`
### Variable-size and fixed-size
@ -78,8 +78,18 @@ For convenience we alias:
* `null`: `{}`
### Default values
Assuming a helper function `default(type)` which returns the default value for `type`, we can recursively define the default value for all types.
The default value of a type upon initialization is recursively defined using `0` for `uintN`, `False` for `boolean` and the elements of `Bitvector`, and `[]` for lists and `Bitlist`. Unions default to the first type in the union (with type index zero), which is `null` if present in the union.
| Type | Default Value |
| ---- | ------------- |
| `uintN` | `0` |
| `boolean` | `False` |
| `Container` | `[default(type) for type in container]` |
| `Vector[type, N]` | `[default(type)] * N` |
| `Bitvector[boolean, N]` | `[False] * N` |
| `List[type, N]` | `[]` |
| `Bitlist[boolean, N]` | `[]` |
| `Union[type_0, type_1, ...]` | `default(type_0)` |
#### `is_zero`