Ledger state associated with a block

This is the Consensus notion of a ledger state. Each block type is associated with one of the Ledger types for the ledger state. Virtually every concept in this codebase revolves around this type, or the referenced blk. Whenever we use the type variable l, we intend to denote that the expected instantiation is either a LedgerState or some wrapper over it (like the ExtLedgerState).

The main operations we can do with a LedgerState are ticking (defined in IsLedger), and applying a block (defined in ApplyBlock).

" Ticked " piece of state, either LedgerState or ChainDepState

Ticking refers to the passage of time (the ticking of the clock). When a piece of state is marked as ticked, it means that time-related changes have been applied to the state. There are exactly two methods in the interface that do that: tickChainDepState and applyChainTickLedgerResult.

Also note that a successful forecast forecastFor (ledgerViewForecastAt cfg st) slot must equal protocolLedgerView cfg (applyChainTick cfg slot st). Thus a LedgerView can only be projected from a Ticked state, but cannot itself be ticked.

Some examples of time related changes:

• Scheduled delegations might have been applied in Byron
• New leader schedule computed for Shelley
• Transition from Byron to Shelley activated in the hard fork combinator.
• Nonces switched out at the start of a new epoch.