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eth2.0-specs
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prevent underflow of previous epoch in all cases

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Danny Ryan 2019-04-11 22:48:27 +10:00
parent 8c32128ffb
commit 6ca550489e
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1 changed files with 3 additions and 1 deletions
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specs/core/0_beacon-chain.md
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@ -702,7 +702,8 @@ def get_previous_epoch(state: BeaconState) -> Epoch:
"""`
Return the previous epoch of the given ``state``.
"""
return get_current_epoch(state) - 1
current_epoch = get_current_epoch(state)
return (current_epoch - 1) if current_epoch > GENESIS_EPOCH else current_epoch
```
### `get_current_epoch`
@ -2338,6 +2339,7 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
# Check target epoch, source epoch, and source root
target_epoch = slot_to_epoch(attestation.data.slot)
assert (target_epoch, attestation.data.source_epoch, attestation.data.source_root) in {
(get_current_epoch(state), state.current_justified_epoch, state.current_justified_root),
(get_previous_epoch(state), state.previous_justified_epoch, state.previous_justified_root),