NewIdentity returns the mana-identities map.

RankByFixedRange ranks by a fixed range r.

RankByThreshold ranks by mana threshold.

RankByVariableRange ranks by a variable range based on ro.

Total returns the total mana of the given identities.

Func type is an adapter to allow the use of ordinary functions as Mana.

Identity is a map between mana value and identities with that mana value.