Update BeaconState rename ShardCommittee

Both structs are now consistent with the spec.

Addresses #100

beacon_chain/types/src/beacon_state.rs

@@ -2,33 +2,44 @@ use super::candidate_pow_receipt_root_record::CandidatePoWReceiptRootRecord;
 use super::crosslink_record::CrosslinkRecord;
 use super::fork_data::ForkData;
 use super::pending_attestation_record::PendingAttestationRecord;
-use super::shard_and_committee::ShardAndCommittee;
+use super::shard_committee::ShardCommittee;
 use super::shard_reassignment_record::ShardReassignmentRecord;
 use super::validator_record::ValidatorRecord;
 use super::Hash256;
 
 #[derive(Debug, PartialEq)]
 pub struct BeaconState {
+    // Misc
+    pub slot: u64,
+    pub genesis_time: u64,
+    pub fork_data: ForkData,
+
+    // Validator registry
     pub validator_registry: Vec<ValidatorRecord>,
     pub validator_registry_latest_change_slot: u64,
     pub validator_registry_exit_count: u64,
     pub validator_registry_delta_chain_tip: Hash256,
+
+    // Randomness and committees
     pub randao_mix: Hash256,
     pub next_seed: Hash256,
-    pub shard_and_committee_for_slots: Vec<Vec<ShardAndCommittee>>,
+    pub shard_committees_at_slots: Vec<Vec<ShardCommittee>>,
     pub persistent_committees: Vec<Vec<u32>>,
     pub persistent_committee_reassignments: Vec<ShardReassignmentRecord>,
+
+    // Finality
     pub previous_justified_slot: u64,
     pub justified_slot: u64,
-    pub justified_slot_bitfield: u64,
+    pub justification_bitfield: u64,
     pub finalized_slot: u64,
+
+    // Recent state
     pub latest_crosslinks: Vec<CrosslinkRecord>,
-    pub latest_state_recalculation_slot: u64,
+    pub latest_block_roots: Vec<Hash256>,
-    pub latest_block_hashes: Vec<Hash256>,
     pub latest_penalized_exit_balances: Vec<u64>,
     pub latest_attestations: Vec<PendingAttestationRecord>,
+
+    // PoW receipt root
     pub processed_pow_receipt_root: Hash256,
     pub candidate_pow_receipt_roots: Vec<CandidatePoWReceiptRootRecord>,
-    pub genesis_time: u64,
-    pub fork_data: ForkData,
 }

beacon_chain/types/src/lib.rs

@@ -14,7 +14,7 @@ pub mod crosslink_record;
 pub mod crystallized_state;
 pub mod fork_data;
 pub mod pending_attestation_record;
-pub mod shard_and_committee;
+pub mod shard_committee;
 pub mod shard_reassignment_record;
 pub mod special_record;
 pub mod validator_record;
@@ -33,7 +33,7 @@ pub use crosslink_record::CrosslinkRecord;
 pub use crystallized_state::CrystallizedState;
 pub use fork_data::ForkData;
 pub use pending_attestation_record::PendingAttestationRecord;
-pub use shard_and_committee::ShardAndCommittee;
+pub use shard_committee::ShardCommittee;
 pub use special_record::{SpecialRecord, SpecialRecordKind};
 pub use validator_record::{ValidatorRecord, ValidatorStatus};
 pub use validator_registration::ValidatorRegistration;

beacon_chain/types/src/shard_committee.rs

@@ -1,10 +1,10 @@
 #[derive(Clone, Debug, PartialEq)]
-pub struct ShardAndCommittee {
+pub struct ShardCommittee {
     pub shard: u16,
     pub committee: Vec<usize>,
 }
 
-impl ShardAndCommittee {
+impl ShardCommittee {
     /// Returns a new instance where the `shard_id` is zero and the
     /// committee is an empty vector.
     pub fn zero() -> Self {